I would use a fitted and cover combo over an AIO if she is sleeping longer. Wildchild or BBH with an extra booster have worked well for C. I have a catnaps honeyboy but only just started using it as it is a large. Am happy with it so far but Cat has retired so you may not get one of them
Never given a thought about night nappies being velcro or snaps but I do prefer snaps in general as they don't snag in the wash and they keep nicer with age. Aslo when they get bigger they can't take them off as easy like FJ said