u/5-0-2_Sub

Toby could've easily shut down Transfem Ralsei in Chapter 5. He's done similar things before - just look at the multiple scenes of characters pointing out the differences between Ralsei and Asriel, and the repeated hammering-in that Ralsei doesn't want to wear the hat.

He could've just had the climbing minigame dialogue say "I prefer being a prince, but it's fun to try new things sometimes...!" or something, and that would be that.

I've just realised the sheer dichotomy in the specific choices of our responses. You can either go "Of course!" and reassure them that they're allowed to be a princess - which is met by some of the most excitement they show in the entire game, before falling back and remind themselves that they can only do this with others' approval - or you can shrug them off with "Nah bro...", making them instantly remove the dress and hoping that will be "sufficient" to appease us. "Nah BRO". Not just a joking, casual statement of disapproval like something you'd say to a friend doing something 'cringe', but one that uses a masculine gendered term.

And let me point out the way Ralsei is stood, with their arms open at their sides. It makes them seem really comfortable, given how they almost always have them held behind their back.

Both of them are definitely blue, that's no question. Rocky's white for the whole movie, but I think Grace builds up to it over time. Maybe they differ in Rocky having Green to Grace's red?

As for mechanics, I think both of them would be centered around one of abilities that let you see more of your deck (scry, surveil, explore, etc.) but through different means - Rocky tapping artifacts he creates (referencing his Xenonite puppet shows) and Grace either being exiled or (ironically) having Heroic.