“What will an x-ray show for back pain?”

In a guy your age (if history of trauma), can show fracture. If no trauma, then early changes of degenerative disc disease or any number of forms of arthritis. There are numerous things that can also cause back pain, even in a young guy like you...kidney stone, for example. Kidney stone may be seen on spine X-ray, as well. If X-ray doesn't answer question, don't be
surprised when your provider orders an MRI.
All the best.

Most bone abnormalities. Usually, that is the first thing you do for back pain.