I've heard of Sofia, but never tried using her. I've used Miraak - The follower mod. To skip bothersome details, it comes with fun turn in questline after which he is recruitable. He has his own set of shouts, which you can modify. His arsenal is small, but uses them often which easily makes him strongest follower out there, without giving him any unique op abilities or goditems. Other than that, I like cheating a bit, and add Raloff/Hadvar as follower through addfac console commands. Sad that game makes them useless after Civil War questline. AS vanilla-vanilla follower, Calder all the way.