Most of my RPs set in the Pokemon fandom universe are all OCs anyway, so I do get what you are talking about though. I also understand that not everyone has the same perspective on how characters act and, while I like the spontaneity of it, I tend to tread very carefully and ask for headcanons first if I'm playing a canon character for someone.
But damn XD hope that RP goes well for you :3
It's going well actually. And yes, I say pseudo-historical since it doesn't follow the events exactly and kind of plays off the "Anastasia survived" myth that persisted for decades after the family was executed. It also has all new fictional characters rather than the real historical figures. Of course with it being that way we have much more room to take creative liberties with things too. It's very different from how I usually do historical RPs, but it's working out well and it's fun.