I own one carpet, an IJ / Jungle jag. Mine is in a 4'x2'x18" pvc enclosure from animal plastics (sliding glass, locking doors, basking shelf). He uses the shelf and climbing space (branches) more than the floor space, but he will soak in his large water bowl and use his ground-level hides occasionally. Jungles and IJs tend to stay smaller than coastals, so a 3' long cage that is taller would suit those types better.

As for temperament, defensive / nippy and flighty as babies.. They grow out of this if handled properly. I still use a hook to let mine known that I am going to pick him up (stroke him first) and he is still flighty as an adult, but does not bite.

As an aside, if you are going to be doing a lot of handling, you might want to avoid getting a jag morph. Mine has balance issues that show when being handled, but can function normally in his cage.