Honestly it's really hard to narrow it down, because it rides like such shit it's overwhelming
It's not porpoising, but if I had to describe it, it would be more like bucking than bouncing. I believe all of the harshness of the ride quality is coming from the trailer wheels and since the WD bars are setup tight, it directly pushes it into the cab of the truck, hence why I found the shocker hitch to be a definite increase of ride quality.
Ride quality improved overall with the addition of the Sumo Springs on the rear, especially over rough/shitty parts on the highway. I believe the rear suspension didn't have enough spring to compensate for the heavy tongue weight. I also noticed an increase in stabliity of the truck after adding them, less chassis roll on tight highway onramps/exits.
When we pulled my trailer with my buddies 2018 Duramax 3500 SRW, his bars were not set very tight at all (you can almost slide the bars on the hooks without having to re-run the jack up after connecting). I did notice my trailer (shorter and a lower GVWR than his toy hauler) caused his truck to ride on his over load springs hooked up - and his toy hauler does not. With his bars being looser than mine, can confirm that his truck did ride a hell of a lot smoother than mine.
Homer Simpson logic says to not run a WD hitch...but doesn't really do anything to help prevent trailer sway.