What should the main power level for this shared world be? Naturally, there will be a mix of power levels, but what should the default power level be?
The difference between, "no default level" and, "mix" can be a bit vague, but I'll try to explain. "No default" means that characters can be any level. "Mix" means that characters can be submitted multiple times, at different power levels. There may be an in-game reason for this, or the creator might just want to offer more options.
I picked, "Mix" because I like the idea of a game-within-a-game, where characters can be different levels but in the same setting. Maybe there are in-game comic books (Marvelous Comics?) where the characters have powers they don't have in the main setting, or team-up in ways they don't in the main setting.