It’s hard to tell, but the photo looks like the truck is a 2500.
They are tall because the coils are softer than the 3500 leaf springs and they drop more under the same weight. The 2500 coil spring trucks have the highest empty tailgate height of all the HD trucks.
Air bags need at least 5 psi in them to prevent damage.
If it is a 2500 then you will really benefit from more than 5 pai in the bags towing since the coil springs are fairly inboard, but the airbags are more outboard so you will gain lateral stability.
If it’s a 3500 then disregard all that, aside from the 5 psi minimum. On the 3500 springs you want to let the springs drop about 1.5” and then use the airbags to hold that height for the best stability.