It's possible from what you're describing that you may be maxing out on RAM, especially if the whole computer is crashing. Have you tried taking a look at the Task Manager while playing to see how much memory is being used when the game is running? It's not unusual for the game to start reaching 4-5gb worth of RAM, especially on a very busy lot; pair this with other processes running on your computer, and you can run into performance issues.
A good test would be to try running a blank neighborhood and see if that ends up being more reliable, at least as far as overall performance. If you use CC/Mods, try removing them temporarily and running the game as well. Additional mods will add to the game's overall memory load. (If you use any script mods, you may want to make sure those are updated as of today.)
With it crashing the computer, it definitely sounds more system-related rather than game-related.