I don't have expansion yet, but from what I understand, the warhorse will be the same speed as the Tan rope bridle (the slow horse), just a cosmetic look to it. If you already have a faster horse (not drog) you can "combine" the warhorse claim and your bridle somehow to get a warhorse look for your current speed horse. Something similar is supposed to work for Pallys/SK and their AA horses to give those the warhorse look.