I always thought you could, but i just read a reply to a question that makes me think that maybe i was wrong. essentially, i tend to spend a lot of time setting up towns exactly the way i want them, so for a lot of my towns i tend to prefer for them to remain in stasis as much as possible

No, Caste Options won't apply with SP turned off, nor will most of the other SP functions you may have set up in an effort to keep inactive sims' lives from changing. When SP isn't in control, sims can do whatever they want, or rather, whatever the game somewhat randomly decides it needs them to do.

If you want the inactive sims' lives to stay as they are now, the best option is SP with strict settings, for example blocking new romances or skill gains or career changes. I use igazor's suggested rotational caste settings, with a couple of modifications, when I'm playing rotationally:

Story-Progression-Rotational-Caste-Settings

These settings have worked out for the most part, with the only difficulties being that when I broke the link between SP and Woohooer, some inactive sims started flirting with each other and causing hurt feelings and resentment. But you can leave the link intact, and any sim with Romance disabled won't be allowed to perform romantic interactions. The middle ground would be to set Woohooer's "Check SP for User-Directed" to False, so you could direct your own sims to do what you wanted, but inactives couldn't be romantic on their own.

Point is, you need SP enabled if you want to have any hope of controlling what inactives do. Even disabling both NRaas SP and EA's SP won't be perfect: sims could still be culled from the game, some could change jobs to become your active sims' coworkers, etc.

This seems to be recurring theme lately. Disabling progression within General Options does not halt progression. It stops the mod from actively controlling it.

I've edited the description of the option here, but am not sure how else to get the point across more effectively.