Hmm. Interesting question.
I think I don't really categorise things this way in my head. Everything is
potentially useful for anything.
However, it seems your larger issue is "how to not get distracted and end up tinkering aimlessly". My approach to that is just to keep it basic, for the cast majority of tasks.
Think if you were mixing on a console. You'd have the console EQ, and maybe per-channel dynamics, like on an SSL or whatever. So I have my standard template set up like that. Every channel strip has (in this order) Quadcurve EQ > PC76 U-type Compressor > Console Emulator. Buses are the same, except with the 4k S-type bus compressor instead.
I also have standard reverb bus, with the sonitus reverb on it, and a standard delay buas, with the extremely humble Sony Simple Delay on it.
And that's what the vast majority of the mix work is done with. I only ever add or change when necessary.
For vocal and bass tracks, the compressor almost always gets swapped out for the CA-2A. For reverb, most things won't end up going to the sonitus, as at some point, I'll start to have a more specific idea about the reverb, but that's how everything gets sketched in. The delay will generally also change, or other delays will be added.
Pretty much everything and anything else will only be added when there's a case for it. By the end of a mix, there'll be all sorts on there. But tinkering and experimenting with unknown factors is very rare
during a mix. I might allow myself one or two moments of that. Experimenting with new plugins, I generally do in downtime messing with old tracks that are already finished, and now aren't going to change.