Ok, I think I have since found answers to some of these questions online, but it did require a bit of research.
I think I am going to go with a system which can boot TOS 4.04 or... either MultiTOS or a version of MiNT which uses the old TOS filesystem. This way there is more driver and accessory support, a few more features. But- within a reboot I should be able to get almost any Falcon-friendly app to run.