So it looks like I'm swaying toward the Duet 3 Mini 5 as few have commented on. This way I can also upgrade ‘if and when’ needed.
It looks like I'll have to wait a few weeks before any more Duet 3 Mini 5's are ready, No Pressure David. LOL
I am most grateful for everyone's input and advice.
No doubt I'll be back again with yet more questions, but for now I think I have a bit of reading to do, to familiarise myself better with the Duet system.
Also any more comments and / or suggestions are very welcome.