I'd prefer the 16 qt until ~500g, and then bump them up to 32 qt. I'm of the belief that if you give them some more room, they utilize it... Most people use 15qt to 500g, except for small hatchlings in 6qt only for a month or two... But note that the bigger enclosure size you go relative to the size of the ball python, the more care you have to take to really fill up the tank with "clutter" and places to hide, so the ball python won't become stressed out in open spaces.
I think fireflii has a great looking tup setup!