Front and back pictures attached
I would do sliding genioplasty advancement along with Facetite and Morpheus8 to tighten the skin to give you more definition
The term 'mandible' implies the entire jawline. Any form of chin augmentation (implant vs sliding genioplasty...with neck liposuction) will improve the front end of the mandible (the chin) but not its entire length. (behind the chin back to the jaw angles) Thus it takes more than just a chin augmentation to create a defined mandible. (jawline)