The whole thing Viv says about being ‘mixed’ still means little when taken into a historical perspective, at least from the point of time Alastor lived. In New Orleans during the 20th century a mixed person could be Ango/Italian (the Italians were not well received), or French/Spanish. It’s only been very recently that non Anglo Saxon groups were considered ‘white’. Him becoming a well known radio presenter during Jim Crow as a ‘passing’ person is also dubious. They wanted singing niggers, not hosting ones.
Viv has stated that the closest anyone has come to his human depiction was as follows:

I pass for white in the states, this dude is just white period. I believe this also predates her claims of him being ‘mixed’.
But this is my problem with Viv, she literally can not keep a consistent story to save her life. When writing a character you need to actually do some research into the time periods in which they lived, what their motives are/were. Too much about Alastor doesn’t make sense when you actually break him down.
* He’s a serial killer, but also asexual? I’ve never heard of a single serial killer who didn’t kill for a reason other than psychosexual compulsion. You could say that he got off on control, or was a sadist, but these types of people aren’t asexual, their wires are just
badly crossed.
* He’s mixed race, but just happened to make it as a famous radio host in the most racially conscious part of America during the most racially conscious time period, where ‘passing’ was very difficult due to census records and the 1 drop rule (Americans weren’t allowed to self identify race until many decades later). Louisiana had many mixed people, but they didn’t typically get ‘bleached’ because of anti miscegenation laws, if anything they’d get blacker, as we see today.
* He’s Creole, but practices Voodoo, which isn’t something Creoles really do, at least in Louisiana, they’re overwhelmingly Catholic. He also speaks no French, at least according to Viv.
Regardless it’s a ridiculous debate when I have to listen to a 2+ hour stream to find out a white looking character is actually black, when that could have been easily incorporated into the story. I had no doubt Vaggie was meant to be Meztizo and Angel was Italian American, because, well, their character traits made that abundantly obvious.