How Does a Face Age?

Late 20 year old male here, main change since teenager I see is the jaw definition. I do see more fat under my chin as well. My face overall looks more feminine. The skin is still tight, no real jowl look. The question is mainly regarding how a face ages, if it is normal that a young face has fat along near the jaw bone between the masseter to chin, and if fat or filler can improve it... OR if it is always an illusion where the real issue is mid face descending, loose skin, etc?