My masticatory muscles are quite thick.

My masseter muscles are quite thick, and because of them, my overall face shape looks wide and angular, like a square. I am afraid of bone-shaving surgery, so I would like to use Botox to reduce the volume of these hardened muscles and refine my facial lines to make them smoother and slimmer.

My jaw muscles are quite developed; will this be effective? I've heard that Botox is completely hit or miss. Is it possible to experience temporary jaw stiffness or difficulty applying force when chewing tough or hard foods after the injection? If so, I would like to know how many days it usually takes for this sensation to naturally subside.

Also, when does it become visually noticeable after being hit?