Maiar

[Elendur]

Could a Maia change its physical form as often as wanted, a few times everyone once and a while, or only once and a great while, or not at all? Does it vary from Maia to Maia according to its power? Because they were not (seemingly) bound to the same physical constraints of Elves and other such people, could they fly or maybe levitate a little? Or do they just have super-physical abilities and strength so they could do incredible things like scale a mountain?

Just a few questions I hope can be answered. I realize that this information can probably only be gotten by speculating different events in the books, but everything helps. It is just confusing not knowing the true abilitys of things like Maiar because it leads to discussions like the Balrog Wings or no Wings thing.