That all sounds like a good plan.

I'm curious about the one critical app you are running that can not move past Sierra. Care to share what it is?

On a Mac since 1984.
Currently: 24" M1 iMac, M2 Pro Mac mini with 27" BenQ monitor, M2 Macbook Air, MacOS 14.x; iPhones, iPods (yes, still) and iPads.