As for Cooler's race, we know nothing about it. We don't know if Cooler is superior to all other members of his race. As far as we know, King Cold was the strongest out of the three, but nothing beyond what we saw was shown/explained.
if that's the case like you said then Frieza would'nt able to be the emperor of Milky Way Galaxy and King Cold wouldn't be a King of the Shapeshifter and Cooler wouldn't able to conquered entire Southern Galaxy. because there are only few member remain in the story and even if there has other member of Shapeshifter they wouldn't able to take challege with Frieza, Kurizer, King Cold. not to mention Cooler.
yes, King Cold maybe the strongest Shapeshifter if there's not count on his family member. either way he would've be killed if he actually fight with any of them.
to compare four of them Cooler considerly the strongest Shapeshifter, in any way of compareson with Frieza's 100% transform he still stronger ever even he's not in transform into his ultimate final form.
but like any other race that no matter how super Cooler could be he still no match for SSJ.