Truck and trailer should look like they are sitting on a rail, straight and flat. Sometimes your drawbar will not be exactly right so a 1/2 inch drop at the front of the trailer is OK. You never want the trailer nose to drop more or to ever be nose up. And when the weight distributing hitch is set right the truck will not squat at the rear but will be level.
With the trailer level you have nearly equal weight on both trailer axles. Nose down puts more weight on the front axle and may overload it.
When the rear of the truck squats it has removed weight from the front axle making steering less effective and can definitely increase the feeling of sway. It also makes your rig much more easily influenced by the bow wave of passing vehicles. Good luck with it, I hope your experiment with the other truck provides some answers.
