General x rays will only show if there is a major issue... Few MD's or x ray techs are trained in atlas/axis measurements/ corrections.

Upper cervical chiros have special measuring tools/ machines, and some chiros will also use use various leg length checks.
Mine used the leg length checks, he did many checks before & after adjusting each time.

But I don't think upper cervical alone fixes all other misalignments, as the websites often suggest..
I think upper cervical is great , but i know I needed more than that alone..