Usually no effect. Scoliosis in many people is a mild condition that stabilized (curvature stopped increasing) when they stopped growing taller in their late teenage years. With mild scoliosis, one does not lose height. However, with more severe abnormal curvatures of the spine, one can lose some height.
Depends. Depends on age and severity. If you are skeletally mature, your scoliosis is likely static, unless it was severe (50 or greater degrees) in which case it will progress by a degree a year. If the scoliosis is severe, it will cause a decrease in height proportional to the angle of the scoliosis.