1st the stuff you need to know when it comes to screen &/or game capture [feel free to skim it if you want], then a quick bit on PlayClaw & another capture app giveaway from Boilsoft [@BDJ]...
If you want to record video there's one set of rules or considerations -- if you want to record what's on-screen without using additional hardware, there's a 2nd set. Before HDTV became so common, & more so before DVDs, quite a lot of people captured or recorded video -- many of their tools & principles still apply, though many people today [including software developers] don't want to bother. HDTV brought complications to video recording, & not just because there are more pixels, but because HDTV brought with it more DRM -- HDTV effectively meant that Hollywood etc. got another bite of the apple, had another, fresh chance with the courts that had already ruled in the favor of consumers, & in many ways Hollywood won.
Now the 1st consideration when you're thinking about screen capture is whether you want & can afford to buy additional hardware, either something that installs inside the PC case or sits outside of it in a box. Encoding video takes processing horsepower, & writing the results to storage takes bandwidth -- the same can be said for playing particularly HD video &/or playing games. What you use for one is taken from the other, which is why as capturing game play has become more popular, so has capture hardware. One caveat is that you generally cannot use HDMI -- HDMI is built around DRM [that's one reason Hollywood etc. chose it for the HDTV standard], so if you use an external box you're often limited to 1080i over component cables [essentially 3 cables with RCA connectors, similar to what's been used for decades for audio].
Even with that limitation capture boxes are popular, because while encoding AVC is very horsepower intensive for CPUs, it's pretty easy for specialized chips [you'll usually find one in tablets & cells with a much less powerful CPU for video playback]. On the flip side, IF you can manage it, recording the same picture with your PC to an editing friendly format [not AVC] will give you better results IF you plan on editing.
That out of the way, to record video you have to write a steady stream of data without interruption to storage hardware. SSDs or RAID setups, or even a 2nd hard drive help, because data can be written faster, as opposed to sitting there, building up at a bottleneck waiting to be written. Any other running processes &/or anything using up bandwidth on your PC's/laptop's internal bus have the potential to interrupt that smooth flow of data -- fine tuning that aspect of things often makes more difference than anything else, including CPU horsepower.
The 2nd thing you have to worry about is the format of the data you're writing to storage. There are basically 2 methods of video compression -- one compresses each frame, but stores each complete frame -- one looks at frames forward & back, recording only the changes in those frames between complete key frames [keyframes can be spaced close together, or at the other extreme, there has been online video that only uses one]. The 1st [often Motion JPEG (mjpeg) or DV] takes less time & processing but makes for larger files -- the 2nd varies in how much processing is required, & how much smaller those video files are. And if that's not enough to worry about, some video codecs [COmpressor/DECompressor] are designed to operate Very fast, mainly for video capture.
The 3rd thing you need to worry about is audio. Audio & video use very different clocks -- if you were to record audio & video separately on a PC/laptop, or in the case of recording playing video, if you were able to simply write the incoming audio stream as-is to disk, odds are very high that they would not sync. Video capture software handles that -- how well, AND how well from different sources varies. You may have to test more than one capture app, and test more than one audio device or source when that's possible. You may also have to get involved with the Direct Show filters installed on your system -- yes, some of the DS stuff effects audio.
Capturing video with audio can take some tweaking to get working on your system when demands are high -- recording lower quality 320 x 240 12 fps video is Much less demanding that 1080p 60 fps video at high quality levels. And because of that 1st concern, writing a smooth stream of data to storage, it often takes a more holistic approach.
Now if you want to capture full screen video, whether you're playing a video you're streaming from an online site or playing a game, you need to try & use different resources for video capture as much as possible. If you're capturing video playing in your browser for example, if you're using your graphics hardware to accelerate that playback, you're taking away from what that same hardware might be able to do for you when it comes to capturing and encoding your video. You might have better results if one or the other isn't using the same parts of your graphics hardware. Different browsers, different capture software, & different capture codecs are things you can try, though mileage will vary depending on your hardware, what processes you have running in Windows, & what software you have installed [again what Direct Show filters are installed, & their merit or priority, can matter].
If you want to capture game play the visual features you have on can matter, as well as the graphics driver version, & whether you try to use something like AMD's Mantle. Software for game capture is designed to be efficient & have a lower impact on the resources you use playing games, BUT, if they were to work well for most everybody they'd have to allow for the types of tweaking I've been writing about, which is more than many people are willing to put up with -- another reason capture hardware is popular BTW. So the developers of that software compromise, meaning that what works well for one will behave &/or perform poorly for another. Many also limit your choice of codecs -- you put up with what they come with, no matter its pros & cons.
The best solution for *you* unfortunately is the one you find best on *your* hardware playing *your* game(s). Glowing reviews are great, but don't expect the same, or even similar, but backup & install one to give it a try, restore that backup, & try another. The reason for backing up is that getting rid of the effects of Direct Show filters being installed, as well as drivers, can take far longer than restoring that backup, & that's only if you monitored every change from that installation so you could put things back. Windows media handling is really a house of cards, easily toppled.
When you have the option try different codecs too, but bear in mind that the video recorded with some codecs will *have* to be re-encoded, while some might need re-encoded to reduce file size. It's not a big deal if you're planning on editing or are after best quality [best quality encoding is SLOW, so capture fast at highest quality possible, then re-encode for quality], but if you're after something quick, capture to the end format you want.
Both PlayClaw 5 & the Boilsoft Screen Recorder are light weight apps. PlayClaw adds a driver, but its built-in codec is not registered with Windows, so no effects there. Boilsoft uses whatever codecs you've installed, which actually results in more registry entries, as those codecs are entered again in a new key, but does not have a driver. Of the 2 the Boilsoft recorder is the safer, but PlayClaw's driver *may* make a difference capturing games. Neither has features for tailoring encoding to your graphics hardware -- with PlayClaw you may be able to limit the number of processing threads -- with Boilsoft you can try using hardware acceleration on/off when you use ffdshow for your codec. If you can use both a graphics card or chip & the CPU's GPU [e.g. in win10 or in win7 with Virtu] you can try using ffdshow set to use the CPU's GPU for encoding, leaving the primary GPU free for the game. PlayClaw 5 gives you more choices for setup, and being designed for games, *might* take less away from your game play.
Boilsoft installs to the program's folder, with a .lic file in Windows\System32, & a folder under [Roaming] User App Data. PlayClaw 5 installs to the program's folder, adds tmb2-v32.dll to Windows\System32, & adds a folder to All Users & Program Data, with a log file in [My] Documents.
If you were interested in trying capture apps, you might backup, install PlayClaw 5, try it, & assuming it works, back up again. Then you could restore your original backup, try whatever else, & if you decided PlayClaw 5 was for you, restore that backup with PlayClaw 5, since it'll only install & activate today. I wouldn't worry about the impact from the Boilsoft Screen Recorder itself, but would strongly advise a backup before installing &/or re-configuring ffdshow.