"Milyenek a fiatal lányok?"
Translation:What are the young girls like?
In this case, I don't understand/see the difference between the two meanings? "Milyenek" / "Hogy vannak" is "milyen" more for the "look" and "hogy" more for the "feeling/mood" of the girls?
Isn't it similar in English?
Milyen(ek) a ...? = What ... like? Milyen ...? = What kind of ...? Hogy? = How?
In general, the answer for a "milyen" question is an adjective and for a "hogy" question is an adverb. So "milyen" asks about properties and "hogy" about states.
In this example, the exact meaning of "Milyenek a fiatal lányok?" depends on the context. It can refer to their look, kindness, intelligence etc. "Hogy vannak a fiatal lányok?" means how they feel or whether they are healthy.