WDH shifts weight
forward on the tow vehicle to shift some of the tongue weight
to the front wheels which helps keep the rear from squatting. Air bags etc. keep the back from squatting by giving TV a stiffer rear suspension.
So they both keep the tow vehicle level and change it's handling, but since they do different things they somewhat address different issues. WDH will help with keeping traction on front tires
because it actually shifts weight
to the front axle
. Air bags will prevent bouncy butt syndrome in the TV better.
+1 on be very carful of what you put in that large rear basket, weight that far behind the trailer axle
is a recipe for sway and poor control. It's just not safe to load much weight that far back in my opinion. Easy to do if you are not careful when you have that much space. Maybe folding chairs or something but I personally would not put anything as heavy as a loaded cooler back that far.