Can scoliosis lead to muscle guarding or tighteness around a specific area?

Yes. Sure, spinal misalignment will lead to muscles being called on in uneven ways. Some muscles may be over worked or stressed by scoliotic curves and react with spasm and soreness. Of course, other causes may be bringing on such symptoms, so it's worth it to get checked.
Maybe. People with scoliosis have more acute and chronic back pain than the average population regardless of treatment. Pain causes guarding. It may or may not be related to the curvature.