It's debatable the typical angle a RL horse archer could twist to the left and still shoot but holding and drawing a bow is much different than thrusting with a lance. Horse archers already can't shoot to their right side which is realistic (assuming they are right handed, the reverse would be true if left handed). Really 'thrusting' with a lance is not very realistic at all as far as I'm aware but I understand there needs to be a balance of fun & realism. If we are talking how RL cav fought my guess is many cav in a real battle scenario were likely 1 handed with maces, flails, swords, spear throwing etc (I'm no expert historian though). I even heard of knights on cav with crossbows (apparently they were the more elite troops).