I agree that the man in the iron mask is the real Jay Garrick. I also agree that Edward Clariss/the Rival is too obscure a character to pull out of nowhere like this. So who is "Jay" really?
My theory: The version of Jay we've seen is actually the Earth-2 version of EVERYMAN. That's why he needs Velocity serum to use the speed force: his speed powers were never drained, he never had any natural ones to begin with. We saw Everyman pretend to be Reverse-Flash last season, I wouldn't be surprised if they pulled the same trick again with this supposed Earth-2 Flash.
They've gone out of their way to show that people who become metahumans on both Earths tend to have the same powers (Cisco, Ronnie, Geomancer), so it's not unlikely that the Hannibal Bates of Earth-2 wound up with the same shapeshifting abilities.
Season 1 made it clear real quick that Wells was Thawne/RF
Season 2 however has kept things rather obfuscated, but as Earth 2 is opposites of Earth 1 in many ways, then why not the Earth 2 version of RF aka THE RIVAL, and why not have the big reveal about him late in the season unlike Season 1 that revealed RF pretty quick