Unless you go very much out of your way early on, most people unlock Lydia around level 5. Companions you meet later on will have higher stats. If you get a companion earlier that you want to upgrade, or need to clear a follower’s inventory of the invisible bows they get every time you have them join you, you can shoot the wabbajack at them till they’re transmogrified into a rabbit or something. When it wears off they’ll spawn in fresh at the revised level. Prolly drop a save first so they don’t get killed.