I made a simple override mod for Mjoll the Lioness to use female animations, and boosted her level cap to 80 rather than 40.

However, in game she still walks like a man and caps out at level 40. I am running UFO, but I loaded the Mjoll overhaul after UFO. What gives? I tried dismissing/rehiring her, waiting, etc. and nothing helps.

Open the esp in tes5edit and check that the changes you made are there. Also check that the formid is the same as the original.

Lolwut. I know we don't know each other man, but I am REALLY not so stupid as to make a plugin and somehow forget to put the changes I made into it. That's the roundabout way of saying that YES, the changes are there. I did not, in fact, make a blank plugin and now miraculously expect it to produce in-game effects.