A lightly-loaded driftboat will draw 4-5 inches. A pontoon/cataraft doesn't really save you much there, although they undoubtedly handle skinny water better.
Ask 10 people what the best driftboat is, and you'll get 10 different answers. Aluminum vs. fiberglass, Willie vs. Alumaweld, the debate goes on forever. But I'd recommend getting the biggest one you can, which is somewhat counterintuitive -- but bigger, especially wider, is more buoyant, and draws less water. I've yet to be on a driftboat where I thought a smaller one would be any advantage.