Are there definite advantages to Botox for trapezius muscle pain and shoulder line correction?

As an office worker who sits in front of a computer all day, my shoulders are always stiff and knotted like rocks, and my trapezius muscles bulge up to my neck, making my neck look short and ruining the fit of my clothes. Even after getting massages, the relief is only temporary and the pain doesn't go away, so I am considering getting Botox injections in my trapezius muscles.

I have heard that the principle is to temporarily paralyze muscles to reduce their size, so I am writing to inquire about the specific advantages of Botox compared to general manual therapy or posture correction. Is it possible to achieve both shoulder pain relief and the cosmetic benefit of making the neckline appear longer?

I am curious if I can really feel a significant change in the raised skin smoothing out after the injection, and if there are any side effects such as weakness in the arms when lifting heavy objects. I would appreciate answers from those who have experienced Botox.