Be careful with lights, and if you build in the mountains, turn your Particle Light to low (Even a mighty RTX 3090 will go sub 40fps during a blizzard if this is set to high)

Other combos to look out for: Any light behind the Dark Wood divider. The complex shadowcast really taxes your CPU drawcall budget, on a game already straining there.

You can also Optimize the performance in your own base by building a certain way. Lots of walls that occlude lines of sight can help. The worst possible way you can build is large, open structures. If you want to build a single large structure, have many interior walls dividing it up.

Instance bloat isn't nearly as big a deal as it used to be. The game cleans up landscaping instances well now, and you'll seldom see it go over 7k unless you're buildling in the black forest (For some reason). In earlier version of the game, it was not uncommon to see 14k+ in big areas.