Al
Run OBS as Administrator. This will enable a GPU workaround letting OBS have 'first dibs' on the GPU processing time, so it can do all of its housekeeping tasks before the game eats the rest. If OBS can't, it will delay and skip frames that can't be composited in time.
DON'T use Monitor Capture. It is the worst performing capture method, and should be avoided at all costs. Delete it and use a Game or Window Capture.
If the mods you use are shader-mods, this may not be possible if they are loaded through injection rather than a modification of the game files (like pixelmon), as generally only one injection hook can be applied to a process at the same time without causing issues (game capture uses an injection hook; window capture does not, but may not work unless you run in Fullscreen Borderless or Windowed modes).
Alright, so I changed over to Game capture, but whenever I record, I cannot find the file, and it doesn't make a log file either, so I don't know what's going on. I tried recording another game to make sure it wasn't only Minecraft, but it seems that the footage for that can't be found ether.
*Edit: I went to remux recordings, and it was showing there, but then I can't find the file in the usual folder after I've remuxed it. I did find it in my recents folder however. But it was still a mkv instead of a mp4 which is what it becomes when its remuxed, and when I try viewing it with VLC, it says:
Your input can't be opened:
VLC is unable to open the MRL 'file:///C:/Users/ahsan/Videos/2021-03-16%2012-20-07.mkv'. Check the log for details.