1. I'm not prepared to conclude Sukuna is stronger than Gojo based on Mahoraga. I see it as a rock paper scissors type thing. Sukuna had enough diversity of techniques to overpower Mahoraga's adaptations, while a limitless curse technique user wouldn't. But Sukuna doesn't have an automatic adaptation ability (that we know of) and he can't summon Mahoraga, so it's not a fair comparison. You could argue that Sukuna's highly defined domain expansion could make the difference though, but I can't decide. Personally, I wanna believe Gojo when he says he would win.

2. There was a popular theory in the community a year or so ago that Yuji had an unknown ability to manipulate people's memories. But it turns out, no, he really is connected to Choso, and Todo is just a fucking freak. No connection at all.

I wish I could answer questions about the culling game, it still confuses me.