Will a frenectomy change my lip shape or smile? If my lip isn’t attached to my gums the same as before, will that mean it has a different shape after? Will my upper lip be more droopy or not stretch the same when I smile? My dentist says it’s the best way

No. A frenectomy will simply free up your lip to function properly with freer movement. You will get used to it quickly.
No worries. The portion of the muscle frenum that is removed in a frenectomy will not affect lip shape, function, lip drape, or your smile. It may, however, assist in maintain the closure of the space between your teeth or reduce the potential for gum tissue loss in that same area from "frenum tug." make sure to have your orthodontic specialist and the specialist who is doing the frenectomy address your "?".
Your . Your lip shape will be unaffected. So your smile will be just as nice as before. So only a defect will be corrected and not traded.