There is only one DCC system, it is the same for HO, O, N 3 rail, 2 rail, etc.
You can get different rated boosters (some built into command stations) to handle different amperage loads. You need less AMPS for N than HO, and you need more O.
With DCC, you use one Command STation, and as many Boosters as you need to support the amperage your layout needs. For example, I have a friend with a very large HO layout who has 20 boosters. He says because of the originally wiring it was much eaiser to add more boosters than rewire, and he doesn't really need that many. I have 3, 8 amp boosters on my system. I use Digitrax and 8 amps is the highest rated.
It would be hard to run an AC motor with DCC but not impossible.. You would just have to put something between the decoder and the motor to control direction.
My friend who runs 3 rail DCC does replace the electronics in the locos with his preferred DCC decoder.
