I can’t speak to running Scrivener, but other folks have that covered, so I thought I’d weigh in on your “extra irrelevant info.”
If it were me, I’d just give them Fedora. I set up my partner’s computer with it and they were fine. They adapted to Gnome like it was nothing, and everything went smoothly.
If you’re worried about the UI, you could use some Gnome Extensions to set it up like Windows (dash to dock, Arc Menu, etc.) or set up a KDE, Cinnamon, or XFCE spin to work like Windows.
Mint is an okay choice for beginners, true, but if you’re setting it up for them and will be their tech guru, any significant advantage is kinda lost. You’re the one who’s going to set up the starting packages and the DE and all that, which nowadays is about 90% of the advantage Mint has over Fedora when it comes to beginners. Because of that, since you’re tech support, you should just set up what you’re most comfortable running support for.