I tow a 25 ft Dutchmen with an F-150 using a Blue Ox hitch. I have over towed 40,000 mile in five years.
Across the CAT scales, my TT weights 6200 lbs. that is 1200 lbs. over the dry weight. That puts 700 lbs. on the tongue, which combined with my family, tools and camp gear reaches the TV max cargo capacity.
Cross winds, trucks, busses and driving habits all contribute to sway. But a properly balanced WD hitch will pull straight.
I think you will also find most folks do not drive straight as an arrow, they tend to drift within the lane. This is exaggerated by the TT. I does not seem to be much of an issue and I suspect it goes unknown to most drivers.
I would think a fifth wheel would pull smoother but it does present a taller wind profile. Most importantly, in spite of the half ton towable hype, few half tons have the cargo capacities to carry load of a fifty wheel.
There are a few half ton models that can be ordered with a super duty cargo package but if you really want a fifth wheel I think you will have to choose a 3/4 ton tow vehicle.