@DIY-O-Sphere thanks for checking for me!
@dc42 thanks for clarifying. I think I'll stick with two D3Minis in that case. I'm planning triple z, x and y on the main board, then the coupler and a cyclops as bowden from the expansion, with the other tools as toolboards. Keeps room for expansion for a height adjustable nozzle wiper or something else in the future if I go D3Mini and I'm not sure if I'll need the higher currents of the 3HC.
Will have to think how best to setup the PS_ON macro and main config.g but all sounds doable 🙂