Quinlan Vos very much came from Legends. He's on screen for about three seconds in The Phantom Menace, and Dark Horse decided to use him in their comic series. He took readers on many a dark journey, establishing himself as a dark and tortured character, so EU fans were thrown for a loop when he showed up in Clone Wars as a happy-go-lucky surfer dude Jedi. Of course Dark Disciple, which is written using scripts from unproduced Clone Wars episodes, gives us a canon Vos that is a good mix of his earlier show appearance and the brooding comics character.
I doubt Dryden Vos is Quinlan Vos, because Han doesn't need much foreknowledge of the Force prior to A New Hope. If Dryden Vos turns out to be a Dark Side crazed Quinlan hiding from the Empire, he'd for sure use Dark Side powers, which would make Han a believer pretty fast. If this happens, his stern belief that no cosmic anything controls his destiny in Episode IV would be negated.