What is the best procedure to tighten my lower face/jaw and double chin? (photo)

Based on the photos I’ve seen, you are a good candidate for procedures like Deep Plane Facelift, Neck Lift, and fat grafting. The Deep Plane Facelift is an effective option to address sagging in the lower face and jawline, providing great results for sagging caused by reduced skin elasticity and gravity over time. The Neck Lift is ideal for correcting double chin and sagging in the neck area. Additionally, fat grafting can add volume to your face, especially filling in hollows in the jawline and lower face. These procedures, when combined, can provide both tightening and volume restoration, giving you a youthful and fuller appearance. That being said, to determine the best option for you, a physical examination will be necessary to make a definitive decision.

Thank you for your photographs. Your overall facial shape and skin quality look good. You have early jowl formation and platysma banding in your neck. If your overall health is excellent, chances are your skin quality is very good at 42. For the best result, and the longest lasting result, a mini facelift with a plication of your SMAS layer in a vertical/posterior position should give you excellent improvement in your midface volume, straighten and sharpen your jawline and smooth your neck. This can be performed under local anesthesia with some sedation and the recovery is fast.

You have the option of less invasive skin tightening with Sofwave which is an Ultrasound based device. It helps with tightening the jowls and neck. There is no downtime.
The other option is to do a mini facelift.
Regards
Dr. J