boyCharlie would be neat because "Prince of Hell" has a much stronger connotation than "Princess of Hell." Like, when you hear "Prince of Hell," you have an image in your head. On the flip side, "Princess of Hell" really doesn't mean anything, because the subversion of the trope is also really common. Like, sure, there are a couple of evil demon princesses, but "actually she's a Disney princess" or just "she's actually kinda nice" is just as common. Saints Row: Gat out of Hell has a character who is almost literally just Charlie, Adventure Time does basically this twice, and Mavis from Hotel Transylvania is this but monster instead of demon. boyCharlie being a pure-hearted dumpling who loves puppies and just wants people to be happy is a much bigger contrast than normal Charlie ever was.
Also, it lets you sexually harass Charlie and Vaggie without any backlash. Like Hazbin is never going to make a joke about a male demon creeping on Charlie/grope her butt/rub his dick on her butt, because the fan base would go ballistic and would light Vivzie's house on fire. But if you make Charlie a male, that changes. You could have male Charlie constantly propositioned by dirty old women or have younger whores grind on his dick while he's walking through the red light district, becoming a deer in the headlights because this has never happened to him before, with male Vaggie having to drag him away and protect his boyfriend from dem whore. Like it's an adult comedy set in hell, there's some edgy stuff that can be do but won't cause the audience would get mad if a woman were to do it.