I have a few minor problems depending on the "world" and how much is going on. I too, have a higher end computer BUT with everything installed and running there are issues at high settings and high speed. I've noticed personally that Seasons and Pets cause the most trouble for me so I have Pets uninstalled and seasons mostly turned off except for story telling. Also Island Paradise, Lucky Palms and probably others have lag due to stuck sims and although Overwatch mod helps there are still occasionally stutters for a bit before the mod resolves it. I mostly play at normal speed as well so there's not a huge issue.
Also, I'll add I have the GTX 980M video card and I think having post rendering on high causes higher incidence of lag in my experience.