Is it required to have LiveSplit window visible in the recording of the run? Or just uploading the splits seperately would be enough? The reason I ask is that if I add the LiveSplit window to my scene in OBS I get a weird and very annoying stutter in the game. If it's just running in the background and I'm recording just the game, everything is fine.

I'm not quite sure, but i'm pretty sure you have to have LiveSplit visible in the recording. If its not visible, it probably makes the run a lot harder to verify.