Would bracial plexus damage cause scapular dyskenisis and neck pain?

Yes. By various mechanism it can happen. A neurologist will be able to help.
Not exactly. The brachial plexus is a bundle of nerves that passes through the axilla, or underarm area. True brachial plexus damage is unlikely to cause the symptoms you describe because the brachial plexus is further downstream and causes symptoms in the arm and hand. Symptoms of scapular dysfunction and neck pain are likely due to pressure on the spinal nerve roots as they leave the vertebral column. .