That part I don't know. I only have the one trailer that I use it on. However, a set of snap brackets can be purchased and have one set on each trailer, or the brackets can be swapped fairly easily with loosening one bolt. However, I *think* the trailer tongue heights would need to be pretty similar to just be able to swap them easily from one to another.
I've never used air bags. That's not to say I don't believe they don't work; they're tried and true, but then again so are WD setups. I guess it's personal preference. I'm not sure how air bags affect weight capacity, though. Most hitches are rated to carry significantly more weight with a WD setup than without. As an example, my Suburban's hitch is a Class IV and the tongue weight ratings are 500lb dead weight & 1,000lb with WD setup, which matches the WD hitch's 1,000lb tongue weight rating when using the spring bars. My tongue weight is right around 980lb. The load rating is 10,000lb with a WD hitch, and 5,000lb without.