Well for me, I want him to look exactly like the Female Titan xD. But there is only a small possibilty that his appearance would change if he managed to eat Annie since his appearance didn't change when he ate the War Hammer Titan.

Eren would remain the same, but would get the ability to encase himself in a crystal cocoon when he’s not in his Titan form.

^He still has the power to encase himself in a crystal cocoon since he also ate the war hammer titan(who has that ability as well)

Are you referring to the manga?

yes

Oh, then I can’t really get into this discussion since I don’t read the manga in order to not confuse it with the manga.

He would remain the same but gain all the memories of the past female titan holders as well as be able to scream and call in abnormal titans.

A sexy bitch