I use a 4'x2'x 15" tall enclosure. I have a circle screen cut out on one end that I place my basking bulb / fixture on top of. I also have an LED strip light inside the cage to provide lighting. I do not use UV as I provide supplementation.
One thing others have not mentioned is that you will want to order a cage with a litter dam...My guy is in a C-Serpents cage and I requested a litter dam (it is about 3.5" tall). BTS like to dig and mess around and often spill substrate out of the cage. Even with the dam, mine manages to strew substrate.
I would go with drop down doors...I got sliding doors on the cage for mine and said substrate pieces get in the track (even with the dam) and cause issues. It's not a huge deal, but it is a hassle.