No it isn't easy to create a young person that has reached the Gap of Adolscency in the contrary you run into the problem zone of entire child perception, you have to hit a certain point the thing about that pretty is just the fact to hide the uncanny valley gap with it.
(cuteness is being used as a distraction method to hide artificialness a doll is never scary)
Mature Babyfaces exactly at the 18+ point doing them right is far from easy you will endup with part younger perception (this allready can be seen as a cultural provocation, especialy with PORN as the TOPIC), without going to jail or being looked from a wrong angle at.
Best example you see
DumbKoala shes on the watch list for a reason and not for nothing banned on several platforms.
Only if you have few skill you endup with such a abstraction of youth (trying to entirely hide the artificial points with blending cuteness) or if you do it fully intentionally (overcuteifieing to get a perfect child hit).
You can easily do this as a Guy from Disney but not as a Human Porn Creator (unless you see no societarial responsibility in your work).
