Each scene is different. A general question could quickly fill a book, cover all cases, and be precise enough to kill vital features that don’t require much power.
I have no idea how your files are created. Sometimes there are many Instances at work, which means the Generator needs to be off if that is the problem. See image.
CAD files typically have fewer of the other options, but I leave it to you to explore with no idea about the file.
Could it be that textures were loaded, and they slow down the CPU? Perhaps use the options of the editor view to sort some bottlenecks—just a thought.
Let me know if I should look into something. I’m happy to do so.
Click thumbnail to see full-size image