Massive lag / low FPS on high end PC

@danikeijzers  Okay, it sounds like the lot you've downloaded from the Gallery is complicated enough to impact performance even if that's not the only issue.  This is fairly common when a lot has a large number of objects on it, especially (but not limited to) career rewards objects and items in inventory.

It's a limitation of the game engine, so there's not much you can do, although you may see a small improvement from Simp4Sims's graphicsrules overhaul.  Among other things, the file's settings lower the frequency at which the game switches between using high and low level-of-detail renders, so there's less to calculate overall.

For Eco Lifestyle, I'd try reenabling it but disabling the eco effects.  Sometimes that takes care of most of the performance impact originating from the pack.