Huge balanced map, dense monsters on hard, dense resources and magic, max wildlands and events, normal pacing, 12 challenging AIs.
I don't finish games, not sure how high I could level. I spent like 15 hours on one game, got to like turn 300something, my sov was level 20ish, but she was a commander with the +40% army exp traits, +60% personal exp traits, +25% exp buff, and +25% faction exp starting trait. I was also playing with all conclaves, farming as much mana as I could, and spamming the +25 exp spell on her as often as possible.
I play with those settings because like I said, I don't finish games. I like exploring the map, killing lairs, expanding my civ, interacting with the other leaders, and I feel like each game is a world that I don't want to "destroy" by ending it. Big worlds full of stuff to do last longer.