I believe theme voting begins a month before the jam starts! In this case, that would be around July 23rd. As for the kind of game, I'm pretty sure you can make any kind you want! As long as you don't start working on it ahead of time and don't use AI to make it.
Also, what kind of AI usage are we talking about? Vibe coding, image generation, brainstorming, building the entire game with AI, or all of the above—which one?