Its never been about integers of 24fps. its about how many frames line up when you have 60hz and take out a certain ratio of frames. similar to how harmonics works in music. Anyway, it is visibly smoother but its not perfect (like harmonics).I actually dropped in to watch a bit earlier and lurk. Quality looks fine; if you were to optimize for the CS:GO side it could indeed use more bitrate or a lower x264 encoder preset as you were getting some (minimal) artifacting on the ground textures and after quick movements. Could help slightly with the League side as well.
I still hold that 48fps is BS. The results of someone taking the classic 24fps cinema framerate and doubling it, then making up complete hogwash to defend it (unless you're playing at 144hz, at which point it IS a full-integer divisor). Since it's not a full-integer divisor of the parent framerate, it will indeed skip every fifth frame, leading to erratic playback which will look stuttery and subtly wrong. You want to stick with 30fps, 20, 15, 12, 10, etc. to ensure smooth and consistent playback.
So yeah, try going to the Faster or Fast x264 preset. I'm not sure Medium would work with that CPU without potentially impacting in-game performance noticeably, but it could be worth a try if you don't see any impact at Fast.
Far as the captures go, just make sure they're unchecked whenever you aren't using them. OBS shouldn't init the capture at that point, and so long as there are only a few of them, it won't significantly slow down the .ini file parser. Personally, I just use a Game Capture set to 'Hotkey' mode for most of my interim games. Only needs one capture then, unless the game *needs* window cap mode to capture properly.
Film 24fps (in a theater) uses a 3:2 pull-down to acquire the desired conversion to NTSC 29.97. 48fps was becoming popular prior to "the hobbit" movie ever coming out.
Anyway, to each their own.