Haven't bothered with the exact meaning of the prefixes since I've mainly used the npc's to create copies for my own mods so far, thus not editing any npc's from the fallout4 esm directly. Some seem to refer to locations or specific quests or factions. Enc might stand for encounter, but that's just a theory I got. But, took a quick look at the Leveled NPC entries (which defines which mobs spawns at which player level), and the npc's that the lists refer to have the prefix enc. Not sure if you've checked that list out, but it's a good way to see how the game throws enemies at you. Like, the list for normal mongrels is LCharViciousDog [LVLN:0007313E] in fo4edit, and links to mobs for level 1, 12, 20, 30 and so on. Sidenote: some of the naming conventions in this game makes me wanna strangle myself, and mongrels is one of the worst I've seen. Mongrels are sometimes referred to as vicious/wild/feral (etc) mongrels in some places, yet a lot of lists for them refer to them as vicious dogs instead. Then there's also the vicious raider dog, but at least they are consistent with naming those dogs "raider dogs" all the time