Sure!
Alright so god of necks right here is gonna tell you that they're rather skinny. I would suggest drawing out a slim face/jaw for the girls, before actually measuring out the proportions. Depending on your style (and for what I can see in it), I would suggest keeping the facial features simple. Perhaps a little detail on the nose, small eyebrows. And the ears at the side of the head after being slimmed down will definitely help put the piece together. I would ultimately suggest to start a drawing like this with the head, shoulders, and chest, and do hair, legs and clothes last. And definitely use references to see what kind of style you want to develop, since you seem like you're on the fence about what you want to pursue.
Hope I help!