I think it's absolutely imperative that a driver understands, to some degree, how EVERYTHING works mechanically on a coach including the air brakes. Am I ever going to fix anything?, no. But, I like to know how everything works so that I will understand what the mechanic is suggesting and know if he is giving me a line or the truth. (And, I'm learning ALL the time!)
In an emergency, Air brakes can be 'caged' if you have one that has failed (the diaphragm) to get you off the side of the road.
To the OP, never, ever, get under a coach with a chassis air system without chocking the tires and blocking the frame. If an air line were to give-way, you will be crushed if you are under the coach.
Some coaches have jake-brakes, pac-brakes and we have a retarder that works a little different. A retarder, on ours, has six settings and can be used manually with the stalk or, I can leave the system on and it will automatically engage when I apply the service brakes. All of the systems work well but I like the retarder better than the two-stage type like we had on our Dynasty.
Safe travels,
MM.