I find it much easier to set up my menus/addons etc. on the desktop. Can I do this and then just copy my config files over the the Mi Box Android/data/... folder? Do Kodi & SPMC use the same structure?
These are the items I have in my Kodi deskop config:
I'd recommend using the backup addon, but yes, I do this regularly with my desktop.
Keep in mind that you may want to omit copying the SPMC/Kodi system settings, as some settings in SPMC are unique to Android.
A few things won't carry over, if addons are set up to store data in an absolute path rather than a relative one or special one that won't work for instance, and there may be some that rely on something installed on the computer to work properly, something like NetfliXBMC wouldn't work since it relies on launching a compatible browser in kiosk mode for instance, but most things should work yeah
What about USB keyboard and mouse
Just copy the addons and the userdata folders and you should be good to go. I do this all the time. From kodi on my Mac to spmc on my android TV.