+ AA6YQ comments below
I should point out that the WSJT-X way of supporting multiple radios is to use multiple instances of WSJT-X, of course that gets complicated if using Commander for proxy rig control is required since only one instance of WSJT-X can expect to use Commander to control the DX Lab Suite primary rig.
+ Since there can be only one instance of Commander running on a computer, if you want multiple instances of WJST-X that each use Commander for transceiver control, then those instances of WSJT-X and Commander must each be hosted on a separate network-connected computers.
+ Alternatively, you can host multiple instanced of WXJT-X on a single computer, one that employs Commander for transceiver control, and the rest using WSJT-X's native transceiver control.
I don't know if SC_WSJTX and SpotCollector work with multiple instances of WSJT-X, I suspect they do as you have used plural terminology with respect to that.
+ Yes, SpotCollector can interoperate with up to 16 instances of WSJT-X.
There should be no problem with having one rig controlled by Commander one or more others each directly controlled by separate WSJT-X instances.
+ There is indeed no problem with that configuration.