Just found out I've been wasting my coins enchanting archery gear for 70 hours on Jenassa....so now im slowly giving her stamina enchanted gear, but how will it affect her?

By the same token, if you gave a follow something that added more carry weight, can they carry more? What of other enchanted items?

I think giving a follower a stamina boosting item is a waste since the followers spend all of their time getting stuck on rocks and not sprinting after you.