Obviously this could change if he runs again but a Twitter-less Trump campaign could very much mean the "spark" of Trump campaigning is dimmed. I also think it's very probable that come 2024 Trump will be showing his age a lot more which could be a contrast to DeSantis.
Very much so. You hear a lot about recapturing the "2016 energy" from online Trump fans nowadays. He couldn't really go back to MAGA now that he has a bad track record- NATO is still around, NAFTA was just replaced by NAFTA 2.0, there's no wall, Hillary wasn't locked up, "the swamp" wasn't drained, and the China bogeyman gave liberal internationalism a shot in the arm. That said, he still has enough of a devoted base to beat DeSantis, but a divided GOP just takes them back to their early 2010s wilderness again. A Trumpist-Tea Party schism would be something to see.