As Zachariah mentioned, there are 4 power masters built into the ZW-L so no need to buy a stand-alone PM.
As far as connection/cables - the command base simply connects to the ZW-L's ground terminal with a piece of ordinary, stranded copper wire. Nothing special. That sends the command signal through the ZW-L and out to the track outputs.
And, in agreement with Zach, that I'd probably wait for the base-3 and Cab-1L as it should be just around the corner and will then be somewhat future-proofed.
And yes, your scenario described should work fine. Remote control of each loop's voltage level, which also allows you to run conventional locos
And either the CAB-1L for control of Legacy/TMCC equipped engines or the orange remote for BT control of those same locos, if so equipped.