Some Vtubers are more personal extensions of the person behind them, other times Vtubers are more so characters. So I think it depends, also depends on what the Vtuber is comfortable with. I've seen successful Vtubers commission sexual art works with their other Vtuber friends. Often there is a layer of separating the Vtuber character/persona from the real person behind them, which is part of why I think a good amount of Vtubers say it's fine for people to have fun with it and make fan art of ships.
Also meanwhile Nerissa is over here liking fanart of her licking the foot of one of her genmates lmao, along with her and Irys making out, and her and Kronii making out as well.