Basically it's what French kings, for instance, used to do in reality. Titles to primary heir, some titles to secondary heirs, consolidate power in the royal line as much as possible

something i'm confused about is like. there's a countess in a duchy i hold. she's good, fine with keeping her and her heirs around, but now that i'm a king rather than a duke does it no longer matter if she's the countess in a duchy i hold? if i give her another duchy does she just move there?