I use two outputs (the A and D terminals) from each ZW to power track loops through the TIU. The B and C terminals power accessories. Previously, I used just one ZW with each terminal going to a track loop via the TIU, but there were times (when I was running 8 trains) that it got hot, so I bought the second ZW.
The LWs (125W), TWs (175W) or 1033s (90W) would all be good for track power. I don’t know much about the BW or Williams transformers. If you are running MTH locomotives, they might be a problem. I don’t see them on the MTH transformer compatibility chart. I have heard the CW (also not on the MTH chart) does not play well with MTH locomotives.
I don’t see a need to have 2 TIU channels for each 75-100 foot loop. You will have two loops on level one and will have two on level two if I got it right. One TIU should handle that (one TIU channel for each loop). But getting a second TIU is not a bad idea. I use one TIU for my layout and I have one spare that I sometimes use on a test track.
