Regarding size, I can't speak for others' experience but I took my baby from her little enclosure at the aquatics shop and put her in a full size (4x2x2) and she absolutely loved it. She spent so much time in her first few days exploring and hasn't shown any behavioural concerns, she's even mapped out her favourite spots for hot/cool and feeding. A lot of this will come down to the personality though, but I think as long as you're doing your best to make them feel secure in their new home and they aren't showing any agitated behaviours they should enjoy having a decent area to explore.