Are you making a fake rock? Really you can use sanded or unsanded, which ever you like better. I think unsanded just goes on easier.
T5 are better bulbs, they are brighter and have better output. What dimensions are you building to and will it have an open of solid top? You'll want your basing platform designed around your lights. T5 with a reflector would be at 10-12" away, less without a reflector.