I find for the types of stories I usually want to tell an intermediate range works best, in that I don't really want God like power to deal with, but OTOH I want people to have somewhat well rounded PCs if they want, which is arguably hard in a beginner level (or maybe at extremely low powered everyone is well rounded in a sense so it depends on how you look at it.)
I prefer slow gain xp, but only if rewards can be provided in other ways. (Personalized storytelling and attention, mainly). I think if you really can't provide that it's good to provide some way for people to feel like their activity is rewarded by the game. But on the other hand, I also think it is futile to try and reward all types of players in a single game in a way that gets everyone's needs met--i would rather just be honest but not shaming about it.
Instead of "be an adult and don't bitch at staff if you aren't able to create your own fun", maybe say "we will only provide limited staff run opportunities for character development, so to be involved with a lot of character development/storylines it is going to require that you hook up with a group that does active storytelling for its members or consider being a storyteller or be willing to be proactive in meeting people ic or oocly, otherwise you may feel isolated even though you will still get the passive xp gain/can do activities to get xp." Or instead of "be a role player not a roll player/twink/min-maxer" more like "XP may be a lot slower than you are accustomed to/you may feel a little weird about having such "bad dice"/low numbers on your sheet, and if you primarily feel motivated by mechanical character advancement then the pace may be frustrating to you. We have chosen to focus on having staff driven storylines that concentrate on developing character /stories/ individually and as a group, and your sheets/power levels are taken into account as we tell those stories." Or whatever.
People are motivated by many different things. Just because someone needs the hope of maxing out their sheet doesn't make them a lesser musher than me even if I personally don't care if I ever get to top tier, or vice versa. It is okay to want to "win" a game however you define it too, as long as the game is set up for that.
It is when someone needs something that the game cannot realistically provide, or if something changes and it can no longer provide, that I think a lot of resentment problems arise, and I wish we had better ways of communicating staff intention/interest than implied shame on players. And I wish more staff felt more equipped/empowered to remove people who it's clearly not working for without needing to think that player is "bad".
So I guess I don't think there is a universal ideal. Just some forethought in what kind of stories, progression, and support will be available and disclosure of that will help set the tools you will use to achieve that.