Movement speed-wise, what is the fastest class? Assassin?
...Or would it be based on bodytype (I guess "super tall")?
Tallness only affects walking speed. Weight affects run speed. How much you're holding affects run speed. The warrior has a passive skill(that can be transferred to any class) that can increase your carrying capacity. The Assassin has a skill that speeds you up directly(the equivalent of haste, more than just movement speed) that cannot be transferred. The strider class has a transferable passive skill that decreases your weight class and increases your speed further(even if you're already in the lowest weight class).