Bubbles: I had bubbles in my tank and salt creep was not my problem, the bubbles lowered my ph drastically, so I wouldn't recommend any bubbles.
Live rock: I read (after I set up my tank, unfortunately) that it is better not to have the live rock touch the substrate. People use 2"-4" cut PVC
pipe buried in sand so you can't see much if any of it and then they place the rock on top of it. They also drill holes in sides of pvc
to allow substrate and any micro organisms to be able to move through the pipe. I already have my tank going but wish someone had mentioned this to me before I had fish in the tank...