[quote=@Guardian Angel Haruki]
Also, in regards to the Madoka lore, are the magi at risk of turning into witches again, considering what happened at the end of Rebellion?
[/quote]
Considering that all AkumaHomura ever did was (presumably) turn all magical girls into normal humans, I don't think that's a concern... not to mention the fact that the Kyubey in this story will take certain 'actions' of his own to manipulate the magical girls to become literal slaves to the Holy Grail War, as they are forced to fight for some makeshift wish-machine their species pull out of their ass for all eternity, even if they die and return to their spirit forms. You know how Saber retained her memories throughout the HGWs she appeared in? It's something like that, except that Kyubey has ensured that there will be no salvation for any of them, even if they do obtain the Grail. But that's a secret for now.

And then there's also the question of whether if the magi of the Fate universe would be affected by Kyubey's manipulations, which brings us to your next question...


[quote=@Guardian Angel Haruki]
And are the masters/magi just magical girls, or are they anyone of all ages and could be male or female?
[/quote]
Nope. They are a separate kind of magical-wielders, existing in a separate reality (the Nasuverse reality) that doesn't incorporate the logic and physics of the Madoka reality. Hence they have nothing to do with magical girls, aside for the fact that they are also being manipulated by the actions of both Kyubey and Kotomine.

But there's one major difference between the way Kyubey is manipulating the magical girls and the way it is working with Kotomine to manipulate the magi - the magical girls are now under Kyubey's control, the magi are not. Kyubey can will them into non-existence should it choose to. The details of that is a lot more complex and speculative, so let's leave it at that for now. lol