WinToUSB Pro was on GOTD yesterday, joining older versions of Win10, Rufus, some AOMEI apps, and DIY methods to create Windows To Go drives. Win10 runs fine on a USB drive or on a VHD [Virtual Hard Disk], with the caveats that you cannot update those copies of Win10 to a new version if/when that requires a Windows (re)install, rather than a hotfix [e.g. the upgrade from 2004 to 20H2], and Win10's setup will not allow you to install Win10 on a USB drive or VHD [hence the tools like WinToUSB Pro etc.].
The original idea was that you could carry your personal copy of Win10 with you, complete with all your software, and run it on whatever hardware was available -- this is because Win10 will automatically search its included files and Microsoft's driver database for any needed drivers, and install them when it starts or boots. In practice however, Win2Go drives don't always work so well, with Microsoft stepping back & no longer supporting them. One problem is that it requires a special, expensive USB stick [if you want/need to use a USB stick]; another is that booting anything USB can be problematic nowadays; and 3rd, with some hardware, files &/or drivers are added that are incompatible with most other hardware. If you can work around those problems, then Win2Go can be useful.
The easiest way to work around the USB stick problem is to use a SSD [starting around $20] in an external USB housing [starting around $5]. The 2nd and 3rd problems are mitigated by narrowing your expectations, i.e. just using it on your own hardware, and not expecting it to work elsewhere. Personally I have a small SSD I bought on sale as a backup for when the ancient SSD in my miniPC fails. I have it in an external housing I also got on sale, and use it as a Win2Go drive until it's needed in the miniPC. And the relatively few times I use it, for stuff like working with partitions or restoring backups to PCs etc. it's been nice to have around.
The WinToUSB Pro web page talks about doing the same sort of thing with Win7, cautioning that it could be a problem because of drivers -- there's no support for Win7 on newer hardware, plus Win7 will not search out needed drivers, & so just won't boot, end of story. And that's assuming WinToUSB Pro somehow works around Win7 not wanting to run on USB drives. You'll find a better approach I think at reboot[.]pro... you'll find info & tools to run modified versions of Windows from USB or CD/DVD using universal drivers. I've even used a Win7 version [small enough to fit on a CD] to run the portable VirtualBox launcher [vbox[.]me], and used that to successfully run a full Windows VM.
The WinToUSB Pro folks also talk about some other conversions that I think you'll generally find disappointing. Cloning a working copy of Windows to a USB drive you'll include whatever full version drivers are installed in that copy of Windows, adding bulk and potential issues if you run it on different hardware -- Win10 on its own will instead add minimal driver sets -- while the software you want to bring along may have its activation tied to the hard disk you're leaving behind. You can clone a Win2Go drive to an internal hard disk or a VM, but I can't seen any advantage compared to just installing Win10 there in the 1st place.
A Win2Go drive normally uses a drive set up as MBR with a small FAT32 partition for both the Legacy & UEFI boot files, & a 2nd NTFS partition for Windows -- the small [~16MB] system & Recovery partitions are not used. To boot on some hardware the disk may need to be GPT [rather than MBR], and/or with the set of boot files [Legacy or UEFI] that you don't want used deleted. Windows generally doesn't like partitions on USB sticks, and partitions just won't work well on some USB sticks [it depends on how they emulate a real hard disk]. You can use a single MBR partition formatted as NTFS, and have the legacy boot files on that same partition with Windows -- obviously it will only boot Legacy mode.
You'll have to use a boot drive selection menu if your device has such a thing available, or go into the BIOS settings to select the Win2Go drive in the boot drive order list for it to boot. When you're done you may need to reset the BIOS to use whatever drive was previously #1 in that boot drive list. Win10's boot loader can modify that BIOs list too -- you may need to reset that part of the BIOS to be able to select any drive other than Win10's boot loader.
To make a Win2Go drive you might still be able to use Win10's own tools, if you have a copy [mountable backup?] of an older version of Win10 -- you'll need to copy these files over: ntmarta.dll, pwcreator.exe, pwcreator.exe.mui, pwlauncher.dll, pwlauncher.dll.mui, pwlauncher.exe, pwlauncher.exe.mui. Win10's tool required a copy of the Win10 Enterprise ISO -- personally I think that's the way to go whatever tools you use, since it will not try to automatically activate -- Win10 won't just see it as migrating your copy of Win10 to another hard disk, counting against how many changes you're allowed before it deactivates. Not being able to use a PIN, not tying it to my Microsoft account, not being able to add my own wallpaper, are small enough prices for running Win10 unactivated IMHO. I use the Insider ISOs for the RTM version whenever there's a major version upgrade requiring a reinstall. If you don't want to sign up as an insider, links are available online, or use something like Windows ISO Downloader -- wincert[.]net/forum/forum/227-windows-iso-downloader/ . Rufus will also download the needed image for you, though I haven't tried that feature myself.
The DIY method is to just use Windows DISM [Google for latest Microsoft docs] *After creating the needed, small FAT32 partition*. With DISM you apply the image, which means basically copying all the needed files from the wim file in a mounted ISO. In this case no drivers are installed -- Win10 will do that on first run -- so it really is universal. You can also use DISM to get Win10 on a VHD. Next, you'd use EasyBCD to add the VHD to your boot menu, if you're installing Win10 to a VHD, or use Windows' BCDBoot to add the boot files to that FAT32 partition on your Win2Go drive.