Do not connect transformers in parallel for a single circuit. When phased, the hots of each are to feed separately insulated blocks. You can have an RW or LW feed a single channel, and that should be adequate for whatever you will practically be running. Before my parents gave me a ZW in late 1940s, I had a single type R, 100 watts rating, running two locos, 2 022 switches, and a #97 coal elevator. I don't recommend emulation.
Agreed. Definitely haven't done that pre-DCS nor plan to with a TIU in between the transformers and tracks.
Ultimately, assuming I keep my existing transformers, my options appear to be:
1. Power each of my 4 mainlines (main level outer, main level inner plus yard, elevated outer, elevated inner) with a separate transformer running each through a separate TIU channel. I'd use the variable outputs for where I want to run conventional. Likely use 2 LWs and 2 RWs. The question there is whether a single LW could handle two trains. Guess all I can do is try.
If that fails, i can
2a. Power 1/2 of each main level mainline with a separate transformer and TIU channel. Then I'd need a second TIU (4 channels for 2 main level mainlines and 1 channel each for each elevated since I only intend to run one train on the elevateds).
2b. Get the 180W powerhouses to increase the output to accommodate two trains on a mainline.
Sound about right?