I have an atomic regulator from GLA as well and I've got to say its one of my favorite regulators that I've purchased from them. It's very well-built and the needle valve allows for super-fine adjustment. They also look really cool!
Regarding bubble counters, the in-line type work just fine. You can hide it in your stand or attach it to the side of the aquarium. It really isn't too big of a deal IMO.
You can use these regulators with a reactor, but to be honest the atomic diffusers that they sell are going to be much, much more efficient than MOST reactors. I had a reactor on my 90G and I recently switched to a 45mm GLA atomic diffuser. I'm using about 1/3 the CO2 (BPS) with the diffuser compared o with the reactor, and i'm getting the same concentration level in my aquarium.