You can't make a direct comparison between the draw weight of different bows without taking the draw distance into consideration. For example, if you have a long bow and a short bow and both of them have a draw weight of 200lb, the long bow will still be able to shoot a projectile with more energy due to the longer draw length.
Any crossbow made out of materials from the Middle Ages will have a very short draw length compared to any bow.
I believe you can get a rough calculation of the energy transferred to the projectile by taking an integral of the draw strength over draw distance.
