Hi Mate!
In response to your general question I'd use Shadowplay. I use it myself and it's a great piece of recording software. It has a lot of options in terms of using a webcam, displaying fps, what frame rate to record at etc. I find it a very user friendly and option-filled piece of software that most importantly doesn't drop you frames. OBS is great however I wouldn't recommend using it, I've had a lot of friends use it in the past and the feedback they gave was 'average' however this was some time ago... Shadowplay is great for recording anything on your screen (even two if you want!) without dropping frames in games and other beefy applications. I also like its simplicity, you can easily start and stop a recording with a mere key press and the video will appear in your desired folder (when recording games and such, this simple addition helps a lot!). It also is designed mainly for gaming, however it literally records anything on your screen, it even automatically selects the resolution and frame rate to be recorded with, based on the application(s) running. In my opinion it is also evident the team behind it have spent a lot of time developing Shadowplay's power and capabilities and are constantly upgrading its features, like the ability to record in 4k! so even though its designed for simple job (record your screen) it is very complex at its core - so that's the practicality of shadowplay, now the file sizes.... A video recorded at 1080p 60fps comes at around 2.47GB I know what your thinking,WOH! but you've got to remember what the file contains, the video is of very high quality, (just mentioned) with the addition of a webcam recording at 720p and a microphone also recording sound. The video's length is also 20 minutes. You can obviously turn down the quality of the video and remove cameras and microphones etc. to take the file down to MB ranges. If however you're not looking for quality and you want very small file sizes, I think other recording software is for you. I haven't actually used play.tv but I'm sure its worth a look at! With applications like screen recorders, editing programmes, OS versions etc. it's all down to personal preference really, yeah one application could dominate the other in power however the user must feel comfortable using it otherwise what's the point, this mainly goes for things like editing programmes though since screen recorders tend to be fairly simple to use and thus users go for 'power'. Also if you're worried about file sizes because you wish to edit the files, based on your specs your pc should have no issue rendering videos of this quality, also keeping the videos on your pc should't be too difficult, the file size seems big at first but when you realise what you're getting out of them and how much you can have on your pc at a time, you won't realise it at all. I have a ton of shadowplay videos on my PC and they don't take up that much space.
Hope this helps - sorry for my lack of knowledge or typos I've missed
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