Females are typically more even-tempered, a chill female neonate will remain that way. Chill males can become major doo-doo heads when they hit puberty and want to breed.
Enclosure - keep it as simple as possible for an adult. These are big snakes that eat big meals and drop big messes. I have no idea how mine manage to get - stuff - on the ceiling of an 18" high enclosure but they do.
Babies are easy to buy online because they're cheap to ship. Adults, not so much. If you can find a local normal/classic adult female you will likely get a good deal on her, plus you get to meet her before you bring her home.