I'm trying to permanently remove several NPCs from the game because I want to take over their home for my own purposes. I've tried deleting the form entry for the npcs, deleting their references in the editor, and deleting their AI packages.

Despite all of these attempts, the npcs keep showing up in game with my mod loaded. I'm only loading my mod and the game's esm... no other mods could be interfering. The npcs I'm trying to delete are also involved with some side quests, but I don't care if these are broken as a result since this mod is only for personal use. How can I delete an npc permanently, so they don't show up in-game ever again?

Delete their entries from the actor list, not just from the world.

I've tried that already... its what I meant by "deleted their form entries". But thx for reply anyway.

Don't delete Skyrim.ESM forms. It's almost invariably a bad idea and overkill. Instead, redirect desired references to what you want out to elsweyr. To remove the reference to the NPC, set PlayerREF as their enable parent and tick the "Set enable state to opposite of parent" flag in the enable parent tab.

That might work... but I cant do this since I already deleted both the form entry and the editor reference. I don't think you can create another npc if you deleted the form for it.

Is there some other way to get rid of them? Could quests involving them cause them to keep spawning maybe?

Have you tried creating a new character?

You can remove the override marking them as "Deleted" with the CK's Data > Details window using the delete key.