"Also, one town is greatly affected by lag since the update (even latest hotfix)"
@red51 OK I think I identified the issue. And I can reproduce it. NPCs will cause a slight FPS decrease as to be expected. But there were many rat NPCs (at least 20 or so). I called Terminix and they helped me remove my rat infestation. Rats seem to greatly impact FPS now much more than other NPCs.
So as a test, went into the basement of the church in my ghost town. I spawned in 10 rats .. and each spawn of a rat decreased my FPS steadily. As I killed them, you notice a big spike in FPS increase as you kill each one. Rats seem to hit FPS more than the other NPCs, even the new ones.