I stated in my post that when I despawn the NPC, I transfer the transform back to the system, so the location is remembered when the player comes back through the area. Theres nothing to stop you from saving a structure that would contain all pertinent NPC data, and then reinitialise those variables from the global manager when they re spawn. In taking on a task such as the one you’ve given yourself here, you might have to rely on a custom solution, instead of hoping for a checkbox that solves your problem. I was just sharing something that might give you back some framerate, while allowing you to have persistent NPCs in the world. Besides all the things you’ve already tried, I don’t actually know any further way to tell them to go into a lower resource usage mode.
Sorry I cant help further, best of luck