I worry about the battery longevity of a MacBook though - about damage from keeping at high charge for long periods from it being plugged in/docked.

With an iMac that isn’t concern since it has no battery. It will last 5 years + no problem.

You can set it not to charge past 80%, which spares you of that idle degradation

Supposedly macOS learns about your use and applies charging rules appropriately. I haven't seen it actually work in practice though, unlike Windows 11 of all things that asked me "You seem to be using this laptop mostly while connected to power, do you want to limit charging to 60% or 80% to preserve battery life?" And reminds me every month that's the case and that it can be disabled.

How often do you travel? Optimize for the typical case.

I actually got multiple computers. Some are a bit old, but still usable. Got a MacBook Air for the rare times that I travel. Using an 27” iMac when I am working from home in village. Using a Intel NUC when I am working in the city.