look at the axle rating of the single axle TT. Usually a 3500#. All the weight over that in the GTWR is assumed carried as tongue weight by the TV, eating up payload weight of the TV. Consider that in your choices.
Loaded for camping (before a weight reduction program in both the TV & TT) my TT axle was almost 200# over its weight rating with the Weight Distributing Hitch. Without the WDH, my TV rear axle was over its weight rating. A WDH pushes some tongue weight to the steering wheels AND some to the TT axle(s). I removed about 50# from the rear of the TV & near 200# from the TT. I always tow with water tanks empty.
My TT is a small bunkhouse model with the bunk storage door.