Stealth with companions

You can find them in several Inns and some are quest-related. Here is a incomplete list of several followers.

Additionally you can buy a wardog for 500 gold in front of the stables in Markarth who is independent of a human follower (you can use both).

You can use a Calm spell on them to stop them fighting. If you don't have Calm (or a staff or scroll or weapon enchanted with calm) you're going to have to fast travel (if you can) to somewhere else, or enter a building etc. Anything to make you go through a loading screen. When you come out on the other side, your two companions should be pals again.

(They shouldn't be able to kill each other, so maybe letting them fight it out will cause them to reset when one of them kneels down and yields.)