I kind of love the fact that from the recording it seems very obvious that Akane got the line because they liked her delivery best and that makes me happy that it wasn't just given to her because they wanted to push 12th Gen in some way. I wouldn't mind her becoming the go-to for that.
The Sexy Cat live performances makes me smile if only because I remember the initial reaction that the only ones with solo lines were the cats, but it seems that it's just that the vocal backing chorus track is just very loud during the verses
Live sounds so different because of it. It's pretty cool that Harunan and Eripon now pretty consistently a solo line in the singles.
EDIT: Also rewatching the MV again, I don't think they changed the pitch of the singing? I think the version that Maachan recorded and probably one other of the girls (Mizuki perhaps?) was layered over it, toning the sharpness of that upswing in the muki part down, making it just sound interesting instead of painful.