If you want to run conventional and DCS locomotives on the same track just wire through either variable 1 or variable 2. Then you can run everything from the DCS remote. Just use the TR button (track) and thumb wheel to vary the voltage up and down to run conventional locomotives.
You can use a ZW to power your layout no problem. I use a ZW with fast blow fuses between it and the TIU on my layout. No issues.