If anything, I advocate for third spaces for trans people. I don't think we should compromise the safety of the majority of women and girls for the few. That said, if someone passes entirely and is in good faith, it's generally not as big an issue to use the opposite sex bathroom. But, my question is not about passing, but about the impact of self-id and these actions in bad faith. Maybe if you or any other QT could illuminate the difference we could approach the issues of sex-specific and gender-id-specific spaces more reasonably.

To address your tangentially related question, transmen may pass better than transwomen in general, but most of the transmen I've known have been visibly female in some way or another, even with a full beard and deep voice. Further, transmen do not pose the same threat to women that males do. From a radfem perspective, transmen are female, and thus entitled to female sex-based services and spaces. A beard doesn't make a human male, as there are females with beards either naturally or through external means.

Onto your next point, The males I've heard of using the women's bathroom who don't transition usually call themselves 'butch' women even though they, for all purposes, look like normal men. That being said, I'm sure there could be a bad faith situation where a male pretends to be a transman, but it seems much less likely to be successful than to just claim to be a transwoman. It comes back to my overarching question of determining Good Faith "True" Trans from Bad Faith "Fake" Trans, which is difficult to determine with self-id.

So by all means make a post about this, I've seen this debate before but it's always good to hear more perspectives. Still, I'd really love if you could answer any part of my original question on this thread.