1st things first, IMHO there are just 3 practical reasons to buy & use a Windows tablet.
One, you want a super portable PC, & don't mind if it's low power or comes with very little storage. In that case you can buy a cheap Windows tablet for the same price or less [I've seen them for $50-$75] than a similarly low powered Compute Stick [a PC in a HDMI dongle or stick] or miniPC. And you get the added benefits of a battery & a touch screen, so you can run it without plugging it into anything.
Two, if you're willing to spend more money, you can get a tablet that works with an *active* pen, giving you the same drawing experience you'd get with a graphics tablet connected to your PC/laptop, only instead of writing or drawing on a panel sitting on your desk, you're writing/drawing directly onscreen. Lots of students love this for taking notes. [Capacitive touch screens are cheaper, Much more common, and for the majority of stuff they're OK, but with most [all?] of these screens you're not going to draw a smooth curve or line using one.]
Three, there are places & situations where you need a touch screen, say in a warehouse or on a factory floor, it's determined a tablet [or tablets] would work, and for whatever reason, e.g. tying into your Windows servers, Windows works better than Android or iOS.
The second thing about Windows tablets is that you probably shouldn't buy one to use as a normal tablet. From a purely practical standpoint, they shouldn't exist, because there's VERY little quality Windows software designed for touch screens. The Windows Store's a mess, and getting worse, with the number of quality apps actually becoming less over time. It's a nice idea that Microsoft has never been able to sell, my guess is even internally at Microsoft, as the store couldn't have been designed by their top talent. Sadly, when it comes to Windows touch screen software, there doesn't seem to be much [if any] reason for hope -- Microsoft's focusing nowadays on bringing bigger name PC games to the store, particularly Xbox titles, and having developers convert existing win32 desktop software, rather than designing something for touch.
OTOH Microsoft does do a very nice job of designing & writing software for iOS & Android touch screens, and they've been doing a lot of work very well, bringing over versions of their Office software. In fact mobile Android & iOS versions of their Office products usually get new features & improvements first, before they may or may not trickle down to the Windows touch screen versions.
How you plan to use a Windows tablet should determine the size & other technical specs. As a very portable PC, 7" & 8" tablets are great, being very light to hold & small enough to easily store & carry. But they only come into their own when you use them like a desktop PC, so ideally the tablet will have mini USB & HDMI together with a full sized USB port. The mini USB lets you plug in power, HDMI lets you use a monitor or TV, while a USB hub [preferably powered] lets you connect a mouse, keyboard, & external drive(s).
Used as-is however, without all that stuff, without good touch software the screen's far too small. You can [and should] increase the display scaling to something like 125% -- larger than that and program windows won't hold enough to be useful -- but we're still talking small, fine print. At native resolution, e.g. booting to a USB stick & trying to work at a command prompt, you'll most likely need magnification. For anything but touch screen apps you'll need a mouse, because even if you have a precise enough touch [& skinny fingers], the capacitive touch screens themselves are not that precise. I don't mean to say or imply that 7" - 8" Windows tablets are unusable -- far from it -- but it's not a pleasant experience without a bigger monitor attached [they will generally drive a 720p or 1080p display]. AFAIK the 7" - 8" screens themselves are mostly 1200 x 600 resolution, artificially increased to the Windows minimum of 1200 x 800. Video & things like Kindle books look OK, but are nicer on similarly sized iOS & Android devices.
Microsoft has found a niche market with their Surface 4 tablet, mainly because of the active pen IMHO -- I think the pen is the reason they can sell their All-in-One. A pressure sensitive active pen lets you draw, write, or paint onscreen with quite a lot of precision. You can buy Android devices with active pens too, but they're limited by the apps you can use -- Windows has more powerful software available. For their tablet -- and similar products that have started to appear since the Surface 4 was successful -- Microsoft added Ink to Windows 10, which in essence is a set of tools to let you draw & write on stuff like pictures, docs, & web pages, along with jotting down notes that can often be used with character recognition to turn them into text, which can then optionally be used by Cortana and so on.
To be able to do something meaningful with an active pen you're probably going to want a screen at least in the 10" range, though you also don't want to go too big if you want to be able to hold the device. While a 10" tablet will be noticeably harder to handle than smaller sizes, a resolution of 1080p lets you increase scaling to 150%, making the Windows desktop a much more usable experience. There's also the question of how much CPU horsepower you want/need -- you're going to want higher end desktop PC power for editing lots of large, RAW images in Lightroom & then Photoshop. Unfortunately you'll pay Very dearly for that horsepower in a tablet.
Today you'll pay around $250 [$150 - $175 on sale] for a non-name brand 10" Windows tablet with an active pen, 32-64 GB of storage, and a lowest end Intel Atom CPU. Name brand versions with 12" - 14" screens will probably at least double that price. OTOH name brand 2-in-One devices -- basically a tablet with a detachable keyboard, or a laptop that can be opened 360 degrees, so the keyboard is on the backside of the screen -- with 15"- 16" screens can actually be cheaper on sale than 12" - 14" models.
Note that there are a lot of 10" - 14" tablets being sold with keyboards but without touch screens. Some are clearly labeled as laptops without touch screens, others are not. I'm not knocking the manufacturers... judging by the models for sale, laptops without a touch screen are more popular than those with, so it only makes sense for a tablet manufacturer to leave off the touch screen & associated electronics and add a keyboard, giving them more products to sell with minimal engineering cost. The problem is that these laptops can look identical to that same company's touch screen tablets, and the seller's ad copy can be less than clear about what you're getting.
Some people may prefer a Windows 8.1 tablet [or really any Windows device with a low powered CPU]. The Windows Update process -- searching for available updates, checking the hardware to see just which files need to be replaced, downloading those files & getting things ready, then restarting to actually replace needed files -- can use enough of the device's available resources to make doing anything else impractical until the updates finish. Updates are predictable and you have some control over them in Windows 7 & 8 -- with Windows 10 home [more common on lower powered devices] updates are more frequent, unpredictable, and you have far less control.
If there are 4 or 5 Windows 10 updates a month [Microsoft just increased the number], as much as 2 months out of the year you'll have days that you can't use your device for up to 3 or 4 hours. And Microsoft just committed to 2 upgrades a year, and those take at least 1/2 a day on something like a low powered tablet. Personally I wouldn't want to depend on something like that, that I couldn't use close to 24/7/365 if I wanted or needed to. Put another way, a Windows tablet can be great as a cheap spare, for those [hopefully] infrequent times a PC/laptop is down, but if you need a PC/laptop every day, without fail, you don't want a very low powered Windows 10 device.
If you find yourself looking to buy a low cost Windows device, be it a tablet or laptop or miniPC, it can be difficult figuring out just what's being offered so you can hopefully avoid disappointment & buyer's remorse. Marketing is by nature cagey... the Celeron & Pentium names for CPUs are still used, but mean nothing like they used to. The Intel CPUs most often plugged into a traditional desktop PC are the i3, i5, & i7 -- you'll see those same CPU names also used with mobile chips that can be Very far removed from their plug-in cousins. Best is to Google with the actual model number of the CPU for information and benchmarks.
Note that the older a chip's design [check the release date] and the cheaper its selling price, the more likely support will end sooner. That can be extra important when Windows 10 is updated so often, since each update can potentially break stuff, and Intel may not want to bother fixing or replacing drivers if that happens.
Unfortunately choosing a device based on its CPU can get more complicated still... a bottom end CPU from Intel is likely a quad core, while a more powerful i3 is dual core, as are some i5s, which are more powerful yet. There are many situations where a less powerful quad core CPU makes for a more responsive device than a more powerful dual core processor, and situations where it's the reverse. VERY generally, stuff that really taxes the CPU, i.e. Task Mgr. showing CPU usage near or at 100%, often [but not always] benefits from more power -- everything else *tends* to favor more cores.
Lots of games aren't highly multi-threaded, so more cores aren't that important -- that's why the Intel i5 is so often favored by gamers over the i7, and one reason why Intel beats AMD CPUs for gaming, even though the AMD chips usually have more cores. OTOH for everyday stuff like web browsing, a quad core Atom may be preferable to a dual core i3 or i5. The age of the CPU design [the release date] is also important, because newer designs tend to have more and better graphics capabilities using the built-in GPU.
Storage is pretty variable. A higher end tablet or 2-in-One might use a SSD, which is great. A notebook hard drive, which is stuck in many of the mid-range tablets & Two-in-Ones, is probably slowest, but you'll have the most room. A cheap &/or small tablet most likely uses a modded SD card attached directly inside. And like the stand alone SD cards you can buy, performance can vary. The minimum amount you should consider for 10 is 32 GB.
Microsoft has finally gotten Windows 8 right when it comes to tablets. The disk footprint of Windows 8 grew too much with updates -- Windows 10 grew too, but when you upgrade to a new version that growth is wiped out. Until now that is, & it's still too soon to say absolutely. Microsoft re-designed the Windows Update process. I saw the benefit when I restored an early backup image of 8.1 that used Wimboot on a tablet, then went through the 175 or so updates that had been released over the past 2 years... the backup was from April, 2015, & originally, by the time 10 was released several months later, 8's footprint on the tablet had grown substantially -- that growth didn't happen this time. The other benefit I've seen is that running Disk Cleanup afterward doesn't take as long, and there's less in the way of leftovers for it to get rid of. If things stay that way, I could see running Windows 8.1 using Wimboot on a tablet with just 16 GB of storage -- it wouldn't be wonderful, but it could be done.
Wimboot itself is a complicated affair where parts of Windows 8 are stored in the compressed image on the Recovery partition. It made updates horrible, both in terms of the time it took & the growth it caused. If Windows 8 using Wimboot can now start out & maintain a 6-7 GB footprint, it now beats 10 in that respect. Even more so when 10's upgraded to the Creators Update [1703]...
With Windows 10 Microsoft abandoned Wimboot, compressing certain Windows files instead using an app called Compact. With 10's initial footprint of ~12-13 GB, Compact doesn't do as much in version 1703 as it used to. Maybe Microsoft felt it hurt performance too much, or maybe they feel that it isn't worth their effort nowadays. The latter could certainly be true now that there are [MUCH] more expensive tablets on the market, usually with much more storage, & those weren't available a couple of years ago.