For the animations part we use MotionBuilder and target all animations to MB’s auto character rig and then catalogue.
A-Pose T-Pose using MB does not matter as you have to set the base pose in the t-pose position to set the MB character rig. Technically speaking it’s much easier to bind pose the character in the A-Pose than in the T-Pose that prevents bunching up in the shoulder and armpit area.