Just want to make sure of something. I'm making a follower who will be dependent on Apachii Skyhair. So I make a checkmark to Skyrim.esm, and the Apachii esm. I then checkmark my mod, the esp, and set it as Active File. That means any changes I make to the game will only take effect is the esp is active, correct? If the esp is disabled, nothing would happen because the master files were not altered

That's right mate