I'm playing through Skyrim again, and when choosing what follower to use at my level, I noticed that the Elder Scrolls Wiki lists Mjoll the Lioness's level as
UESP says this as well.
So, if I'm level 28, Mjoll should be level 35.
Are there any other permanent followers with a level that's different than the Dragonborn's? This is assuming that the Dragonborn's level is currently within the follower's range.