The Black Simmer

Yea, this happened on my last pc when I tried to merge cc and also the game didn't run any faster either so I refrain from merging cc. I know this doesn't really help, but honestly If I were you If you don't have a high performance PC but you want it to run smoothly for your household and maybe a couple of other lots you have built, id just build the lots to my satisfaction and then use tray exporter to export these FEW lots (1-3) and then export those 3 lots with cc into another folder.

then I would remove my original mods folder from the Electronic art/The Sims 4/ Mods

and replace it with ONLY the mods used in those lots.

You should be fine to keep all of your CAS mods if you want. I wouldn't worry about those too much .

I hope this kind of helped