The sign-up survey probably acts as a preliminary screening. I'd assume that they'll want a wide variety of players with different styles, progress, equipment, etc. After that, it's reasonable to assume that the selection would be randomized.
Gameinformer says only characters past the extremely exclusive threshold of level 10 were recommended.
lol
It might actually be challenging, who knows? For me, my enchanted Daedric set of armor and weps makes me an unstoppable tank. But if I go for light armor and don't use my uber weapons, some enemies can be quite lethal. So, so long as you don't intentionally uber your character, the difficulty should be fine.