Twists: Lower lumbar twists such as Jathara Parivartanasana should be minimized, if not avoided, for lumbar scoliosis, OR, should only be done in direction, which does not emphasize the curve.
As for Thoracic twists, my reading is that when twisting toward the concave side, that should be more of a lengthening, and when twisting towards the convex side, it should definitely be a lengthening, strengthening, then twisting.
Twists: They should be done to optimize straightening of lumbar curve. That is with left lumbar curve do the pose with hips to right side and pelvis moving toward the foot.
Thoracic twists: In general I recommend working from lower edge of the curve and lifting to straighten these curves. Concave side will tend to have shoulder lower therefore elevate that side from pelvis to shoulder. Convex side shoulder will be higher therefore leveling shoulders will require strengthening of latissimus on that side.