Thanks again to all the responders.
I did end up reinstalling Twallan's Master Controller, Story Progression, and Overwatch, because their benefits outweigh my mod misgivings.
I've started a household in Moonlight Falls, and the game seems to be running okay so far without any RAM tinkering. I'm not thrilled it still takes 2-3 minutes to load the game, but I can tolerate it. Hopefully that isn't bad for having 9 expansions, 4 stuff packs, and a bunch of old store junk installed? (It still loads much faster than when I used to have tons of .packages)
Thanks for the "Save As" tip. It used to be so frustrating to lose a legacy. : (
My town indecision was because there has been so much more content since Generations, that it feels overwhelming. So, instead of trying to track it, I'll just change towns frequently until I get re-acclimated. I'll raise a fortune-telling supernatural family in Moonlight Falls, then have a performer family in Starlight Shores, and start a rancher family in Appaloosa Plains. If I do it like this, I think I would just need to check to make sure each town has a festival lot for the extra Seasons stuff, right?
On a side note, I checked the Exchange to see if any of my old creations were still there. (I think I uploaded about 4-6 houses in the past?) I was expecting that nothing would be left, but something I uploaded in October 2010 was still there, which made me happy!