Does the lower back affect posture as well? lets say your upper back posture is good, but at the same time, the lower back posture is not good, does it affect height ? can you improve lower back posture for height ?

Of course, stooping or bending over at the upper spine makes one shorter. The lower spine should have a normal amount of concave curvature to protect the rest of the spine. Too much curvature will cause problems of pain mostly&chronic low back pain often causes stooping with loss of height. Corrective exercises will improve excess lordosis. Being evaluated at a spine clinic will assess your spine