Sunset Valley is the least problematic town for me. What is your lifespan so I can get an idea of how long it takes for you to get to the third generation?
Have a look through https://www.nraas.net/community/TIPS-FOR-BETTER-GAME-PERFORMANCE for some ideas. I don't do everything suggested but there are several things I do religiously and the only thing I can complain about it is the time it takes to load and save after I have played several generations (I play a slightly modified normal lifespan so after about 150 sim days saving and loading becomes a little tiresome).