Denford Triac VMC with ATC Conversion / Fix

[JAZZCNC]

Does this controller work with Mach 4?

Yes and No.
Yes there is a Plug-in for M4 but it's still in Testing phase and not yet 100% stable so I'd recommend you don't Bother.
The good thing is with M4 you can run it along side M3 without interfering with each other so testing M4 is easy if you want to try it and won't wreck your normal working M3 setup.

Which of the modules is the encoder module? Are you able to link it please? Also, how would I know, what do I look for that might be able to indicate if its needed or not?

I've had a quick look at schematic and it's a DC spindle with no sign of encoder so wouldn't worry about it.