I love the back of the heart as well!
I'm not a PQ expert at all, but personally as the coloured fabrics are patterned in some way, I like the fabric to not be distracted by quilting, plus I also like the wrinkled look the unquilted fabric gets when its washed; it adds its own texture. As for rules about batting and maximum distances I've no idea, and/but I am a rule breaker generally