For example, the file Armor_001_Head.sbactorpack has the RSTB path "Actor/Pack/Armor_001_Head.bactorpack".
Actor packs are loaded from here by default.
For example, the file GameROMPlayer.sbactorpack has the RSTB path "Actor/Pack/GameROMPlayer.bactorpack".
Resident actors (actors that the game keeps loaded at all times) are loaded from here. Some actors are hardcoded to be resident, but others must be listed in ResidentActors.byml in order to be loaded from here.