Iroha's Doppel, Giovanna gotta be my favourite Doppel from the anime
For what it's worth, Giovanna is interestingly enough, a witch or a half witch trying to protect her human from the reality of the world, which is actually a first and interesting outlook into the inner world of witchification/despair, considering what she said about how "Iroha was tortured with nightmares of her friends becoming witches", so she trapped Iroha in an utopian dream where they can be magical girls happily without the threat of becoming witches (The loads of grief seeds from one witch killed so no shortages of grief seeds will be a problem) and a world where Ui exists, even as a plushie, and freed of her illness
I now realize how this is quite similar to Homura's witch in the soul gem (chick in the egg) situation which is the main plot of Rebellion, both cases are dream scenarios dressed up to hide the rotting curses beneath, the difference I believe is that Homulilly herself doesn't get much of a personality in the sense that we don't get HER lines on things but more of Homura's lines on things, there's never a scene where Homulilly is shown as a connected but separate entity altogether
Magia Record does play with the trope of "Inner Devil talking to/existing together with pthe real self" with Giovanna/Iroha and Yachiyo/Campanella (Campanella directly converses with her human too)
Magia Record has its issues but it showcases such an interesting aspect of witches or those close to being them, Doppels
I want to chew on this ask for hours bc I love it so much. I love Doppels/Witches and their relationship with their magical girl selves SO MUCH!!!!!!!!!!
I really love how Doppels represent radical self-acceptance. You have to make peace with ALL of yourself, even the parts you want to hide, if you want to coexist with and master your Doppel. Otherwise it will consume you.
Rebellion delves into this idea too. Sayaka is shown to have fully integrated with and mastered Oktavia, her Witch self, thanks to being part of the Law of Cycles and undergoing a lot of character development.