Just use one PH180 for now. That should provide you with enough power for the number of engines you want to run.
If you are running two loops, then you can put one PH180 to each loop. REMEMBER to isolate the center rail(s) between the two loops with a plastic track pin or gap. You do not want the two PH180s connected via the center rail. Outside rails (ground) is okay.
You only need one Cab2.
Without DCS, you can run the much easier bus wiring. In the diagram below the PH180 plug is cut off and wired to the track. You can use the TMCC lockon instead. A fast acting fuse is added, but some say it is not needed because the electronic circuit breaker in the PH180 is fast enough. I would use one. I also highly recommend you add the TVS to protect the engine electronics. There are many posts here on the forum discussing the benefits of a TVS.