Our 1989 GV has leaf springs, disc brakes, and an electric assist motor for powering the master brake cylinder.
NO AIR BRAKES. Definitely NONE. (it is a relatively strange arrangement)
Do I have to remove the wheels in order to replace the disc brake pads? What drawings I have seem to indicate the rotor and disc pads & calipers are inboard of the wheel & rim.
I believe you have the Hydravac system that uses the power steering hydraulic pressure to assist the brakes I had the same system on my dually. To answer your question, the wheels do have to come off to lift the caliper up to change the pads.
I'm not aware of any drum or disc brake that you do without removing wheel.
On an RV, I wouldn't think they exist, but on other vehicles they do. Just Google inboard brakes.