If you have crossed the age of 18 than no jaw corrections can be done orthopaedically , either we can go for jaw correction surgeries or camouflage with braces treatment

Go for orthogmathic surgery

Braces at your age can retract align and reposition your teeth if need back Jaw movement will need surgical correction that too if needed

Hi! Orthodontics or braces is for movement of teeth, not of jaws. Jaw movements are not possible without surgery. (Orthognathic Surgery) Braces can change teeth position and change your smile confluence to an extent. If you are not happy with the position/shape of your jaws, you need to see an Oral and Maxillofacial Surgeon who can advise whats best for you. Second part of your question : Severe muscle contractions of the jaws can cause you to have a traumatic bite or attrition (grinding or breaking of teeth) or make you have a squarish face because of the bulky muscle. Best Regards.