YouTube. He uses OBS like everyone else. You can record and stream separately, which seems to be what he does. Does wrong... as with everything. Use 2 instances. I've recorded locally in 4k and streamed at 720 before with 2 instances of OBS. Doesn't take any effort. That way he could remove the pathetic e-begging source across the top of the screen and that dickhead doing the "commentary" when uploading to YouTube. If the game play was even good he could have potential licensing options for it in the future. No one wants footage with his crappy layout and fugly stroked boomer face, acting like playing everything is effort with commentary of "look at this", "I'm going over there" and "i died, ack ack ack".
The YouTube channel is how to draw people to Twitch. Use it as free advertising with short, funny/interesting clips to get people to the stream. Instead he spams blocky, out of context crap expecting to be picked up by the "bigger losers than you" algorithm. If you found one of his videos on YouTube would that draw you to Twitch or would you "Don't recommend channel" it?