I have Timbrens on my Ram 2500. They set 1" above the axle unloaded. I have a 5'er with an 1800lb pin weight. Without the Timbrens the rear drops 2", which is fine since the rear is already 3" higher than the front. I installed them to gain a more stable ride. Less lean in the corners. Nice thing is they're a 30 min install, no air lines to possibly leak and the empty ride is the same.
They shouldn't affect your WD.
If you go with air bags then you need to load the cart in the truck, air up the bags to bring the rear back to it's original height. Then hitch up and set the WD to the TT's TW. That's how I did it when I had a TT with a different truck. I had to put a lot of gear in the truck and found that having to use 1000lb bars for the 450lb TW caused a stiff ride. I went to bags an bars rated @400-600lbs. Rode like a Caddy.
When I had the bags on the other truck I didn't have an on board compressor so it was always a PITA to air up or down. If I had the money I think I'd go bags and compressor over Timbrens. The towing ride was smother with the bags. Two different applications for sure, but I think the bags may give a better ride since the Timbrens are stiffer. Timbrens are definitely a cheaper way to go with decent results.