Poorly defined jawline and chubby cheeks when I smile, what could improve this? (photos)

Buccal fat excision is an appropriate surgical procedure for patients that of overly full and wide cheek areas. In common terms, it is good for patients who have chipmunk cheeks. In reviewing your pictures, is difficult to tell if you're a good candidate because your cheek area is slightly full but not overly full. Liposuction can further slim the face. You are a patient that would need an in person consultation for a complete evaluation and explanation of the positives and negatives of these procedures in your situation. I hope this helps.

Chubby cheeks are commonly hereditary and could be present even in patients with normal to low normal BMI. Chubby cheeks also tend to be resistant to diet and exercise.
Buccal fat removal is the plastic surgery procedure that helps to correct the fullness of the lower anterior cheeks. The video bellow helps to understand who could be a candidate for buccal fat removal.

A define jaw line is present when there is no fullness (fat) underneath the chin and there is an strong jaw bone. When the jaw bone is not prominent, it can be enhanced with soft tissue fillers like voluma with minimal downtime.