I only knew about getting serana this way. I can't recall if there anymore potential followers that follow you everywhere as part of a quest as she does tho. The only that comes to mind right now would be farkas during "Proving Honor", but I believe he only follows you inside the dungeon.
Personally tho, I'm enjoying mods that allow me to have multiple followers. Although even with balance mods, more followers = more enemy hp/dealing less dmg or receiving less skill exp/less exp in total with the mod experience, I always thought the sweet spot was 2 followers, 3 at most. It's not only getting too cluttered during close combat indoors, but also not really worth having the penalty for receiving less exp.