Would a Sliding Genioplasty and Submental Lipo help me achieve my goals? (Photos)

None of them; a sliding genioplasty is pointless or almost is in your case, you'd end with an over prominent chin; lipo is not the treatment of flaccid neck.

You have deep marionette lines due to a familiar trait likely affecting all females in your family tree, this has difficult if any solution.

Sorry for the bad news.

Jawline and submental liposuction would improve the contour and definition of your jawline. The amount of jawline projection that you need is about 5 mm so a sliding genioplasty or implant would achieve a good result.

To create a more V-shaped facial contour, you could consider jawline enhancement, either with dermal fillers or a chin implant, to refine the chin and jaw proportions. For a sharper transition between the chin and the neck, VASER liposuction to the under-chin area can help remove excess fat and improve definition. These procedures can be performed separately or combined, depending on your goals and anatomy.
Best,Dr. Süleyman Köken