I started with a DigiTrax empire builder, it can run 22 locomotives, I quickly found out that even when you have engines MU'd together, sitting in the staging yard, they still use up those 22 available address. So if I had 7 trains in staging, each with 3 locomotives on them, that would only leave me 1 locomotive I could run, without un MU'ing a consist. It was a PIA, so I had to upgrade to the Super Chief, that gave me the ability to run 128 locomotives, (I think.) Again, not all running at the same time, that would need additional power supplies, but just being consisted together, takes up the slots.
So if I'm understanding correctly, I could have 40 RailPro equipped locomotives on the layout, consisted in pairs, (so 20 trains ) and I could only RUN 6 trains (12 locomotives ) at once? I'm designing this layout for operations, maybe 6-8 operators during an op session.