Shortcuts to saving CPU and GPU?

I am currently building a semi linear horror game that is somewhat demanding, especially since I plan to port it to an ipad/iphone. Are there any shortcuts so that the software is not running so much all at once? Mostly I have a lot of buildings that are on the map all at the same time, so far I’ve been attaching everything to the terrain since from a distance it doesn’t render everything at once which helps a lot, is there any other tricks similar to this?

Use oclusion cullin, is a menu, it will make to stop rendering anything that is not on the screen