From what I read it's more like RubHugKissLick and I can imagine biting and slurping but chomping sounds like something Chinatsu would test on Akari~n! so...to be continued?
Kyouko is a top because Yui is kinda tsun with her feeling for Kyouko and she tends to be the one doing the blushing whenever Kyouko do the mushy talk.
I've come to the realization that nobody actually knows what canon Yui's personality is like. It's a complete mystery.
She's just a typical high school gamer with a small circle of friends not anti social but dosent go out of her way to interact with people it's just weird because she is a high school trope in a middle school manga.