LOL. That's profiles to you ;]
If you could either tell me the plot in a few sentences of send me a draft I could gladly help with suggestions or anything :3
I guess you should choose the setting that allows a better developing for your plot. If you want vehicles with a certain degree of "technology" so to speak. Then medieval onwards. But if you're willing to have good ole sticks and bones that break bones then any but modern or futuristic. And so on. Choose the one you feel you can work better with :]
Or steampunk xD Everybody loves steampunk :p
Again, factions are another thing you must be comfortable with to work properly when the RP begins :]
Quality standards. How long and how often do you want people to post? Is it sandbox or do players stick to a certain storyline? How many paragraphs minimum for each section? Is it a cooperative RP or a competitive one? So on and so forth. All this info will let players know beforehand if they will be comfortable with the RP :]
Powers... Could you delve more as to what sort of powers xD *looks at superhero profile*
Also, yes, I'm able to help you out :p