have met a few non-binary people who I can’t tell what their ‘biological sex’ is....
In terms of how that person moves through their everyday life - how people refer to them, what spaces they’re allowed into - what do you think should happen?
I think males should always use male spaces, as males as a sex class present statistically a higher threat to women - not just that they are more likely - statistically - to be violent, but also that they have penises and are able to impregnate a woman. I know it sounds brutal, but we are discussing exactly these brutal truths, these are why we have societal rules. We exclude males from spaces where females are vulnerable partly for reasons of dignity, and partly for reasons of safety. I also find males in a small confined space alarming, doesn't matter how they dress or present. (And I would wager that there are very, very few transwomen or male non-binary people who 'pass'. It's very hard to hide all the many physically male characteristics.)
I personally don't care at all where transmen or females who call themselves non-binary go - they represent far less of a threat to women, and in my experience transmen who pass still don't set off my 'man alarm' as males do. I would note, however, that they may be putting themselves at risk by using male designated spaces, but that is their choice.
As for pronouns. Generally, I'll try to be polite. But I will not refer to criminals, rapists, etc who are born male as females. I just won't. It is deeply offensive to me that a rapist asking his victim, in court, to use female pronouns, is respected. I also will sometimes just avoid using pronouns, for the reasons laid out by the fabulous Barracker, here:
fairplayforwomen.com/pronouns/