I’ve used dk weight yarn and crochet hook 5/0 for this project, but I’ve had an experiment switching the crochet hook sizes. (yarn weight stays the same)

using 4/0 hook: a top fit blythe and licca chan doll
5/0 hook: a top fit Jenny, Pullip doll
6/0 hook: fashionista barbie, or late 90s barbie doll
7/0 hook: vintage barbie from 60s to early 90s(These guys have wider chest)