I didn't have MCC until after I was in the 4th generation of trying out the Disney Challenge So maybe a couple years after I got the game. I basically just did what CherryBerryCloud said. Basically only played non-main household (other than upgrading them, aging kids, etc) when trying to find them an SO and get a few good shots. The rest of the townies were basically left alone, though. It was just descendant families and such. Even after MCC, I still do this sometimes, because I sort of feel how Sharonia does. Again, mostly just for relatives and such. I get attached to these Sims and families and I want to see them do well. I won't micro-manage enough to keep the game stagnant and keep them from dieing from things (if it unfortunately comes to that) other than old age, but I at least want to set them up. Also to fix CAS. Even without CC in the game, sometimes they end up with questionable outfits.....
Also, with the overheating thing I think it may be your older laptop like you said. I had an old laptop when I was playing Sims 3. It would make all kinds of whirring noises and get quite hot (and this was without a single CC or mod), and I had to play it with a fan underneath my laptop. My current one is getting old by technology standards, but it still handles quite well. Sometimes loading is a bit slower, and my PC snob bf is like "Do you not have a solid state?!" ("uh... Sims is the only game I play that makes my system actually work....?"), but I still deal well. I pop on here or scroll FB or something.. lol