To start with the conclusion, if you are planning to have orthognathic surgery later, such as protruding mouth surgery, maxillary surgery, mandibular surgery, or double-jaw surgery, absolutely, absolutely do not undergo preoperative orthodontic treatment.
This is not just my opinion. It is what every oral and maxillofacial surgery director I consulted for orthognathic surgery said.
And even if you undergo extraction orthodontic treatment, there will not be a dramatic change. You will not become Jang Dong-gun or Won Bin. Absolutely not.