Just bought a TT and don't have a TV for it yet. One friend, who tows a lot of heavy things, recommends nothing less than 3/4 ton P/U. A mechanic friend, who we will be camping with, says his 1/2 to...
1/2 ton can tow a good size TT and be within ratings. You just need to compare the weight of your TT to the truck ratings you are interested in. But if you even think you may buy a larger TT in the future you might as well start off with the truck to pull a larger one.
My last 3 trucks have been 4x4. But only because dealers have very few 4x2 in the trucks I want (loaded Lariat or King Ranch F350). Have never used 4x4 while towing.