Now, even though I read Fizz's lore I am not able to be certain if it is still canon, but my question comes with more what is he?
Is he a Vastayan or a Yordle? I don't really think it is possible to be both with the way 
treats Yordles so differently from other Vastayans but he doesn't necessarily look like the other Yordles we know, not to include that he doesn't even really come from Bandle City. Is there anyone who has any clue on what he is in the lore?
He's a god damn enigma. I can tell you he's no vastayan at least.
Apparently he and Nami are officially Vastayan
He is a character of the game.
He is not a Yordle, at least wasn't before the new lore (source here and here). Keep in mind his lore has yet to be updated, though I think League no longer existed when it was released, it is really short compared to the new lores, so it will probably be reworked eventually. I've seen talk about Tahm Kench's unique taunt implying he was the cause of Fizz' people vanishing, but idk.
Personally, he looks to different to be a Vastayan, so I would bet on being another, not yet revealed race.
He's something that Riot will eventually figure out, once they get around magical sea creatures or yordles once again.
