I see I'm obligated to address the sports question too. alrite, let's get into it
I remember a few years ago seeing a video clip of MMA fighter Fallon Fox (male trans identified) beating the living shit out of a female opponent, really horrific, smashed her skull in.
first, the sports question is actually the one area where there's data suggesting that trans women should be excluded from competition with cis women under some circumstances. there was a Springer paper in 2021 suggesting that despite a noticeable decrease after a significant period (I don't remember exactly iirc the test subjects ranged from 1-5 years on HRT or thereabouts) that there's still a significant advantage - again I don't remember exactly but iirc it was something like trans women testing around ~90th percentile for all women in things like average lean body mass and strength. here's the paper if anyone wants to read it:
Males enjoy physical performance advantages over females within competitive sport. The sex-based segregation into male and female sporting categories does not account for transgender persons who experience incongruence between their biological sex and their experienced gender identity...
link.springer.com
Now, the authors of the papers do specifically state in their conclusions that
...it is clear that different sports differ vastly in terms of physiological determinants of success, which may create safety considerations and may alter the importance of retained performance advantages. Thus, we argue against universal guidelines for transgender athletes in sport and instead propose that each individual sports federation evaluate their own conditions for inclusivity, fairness and safety.
Basically, the advantage is strongest in sports relying heavily on upper body and explosive strength, less pronounced the further you get away from that. Side note: this should be obvious, but the decreases in mass, strength, etc do make it virtually impossible for trans women to continue competing against cis men.
Now, that was one study with 46 subjects. Obviously more needs to be done. But especially in sports that involve contact - MMA, American football, rugby, etc - I'm 100% fine with a policy of caution. I'm also fine with a more conservative policy in sports like weightlifting that are heavily reliant on pure and/or explosive strength. A New Zealand trans athlete named Laurel Hubbard, who began transition in 2012 at the age of 35 for reference, was allowed to compete at the international level in the women's super heavyweight category from 2017 until she retired following the Tokyo Olympics. I thought and still think it was a terrible decision, based on optics rather than fairness or sound policy.
Ultimately, there's always going to need to be some arbitrary decision about testosterone levels (or rather t/e ratio, which is how it's measured) based on the available data. That's what happened with Caster Semenya. The issue was never just, as Benny would have it, her chromosomes, it was her testosterone levels - the IAAF wound up basically saying if you take medication to knock your T below what we've decided is fair, you can compete. But cisgendered men and women also have varying testosterone levels. Part of elite athletes' genetic talent is precisely higher natural T than the average person. That's not discussing the validity or not of using T levels as a deciding factor, only saying that any number will be arbitrary.
In a more abstract sense all "fairness" in sport is ultimately a compromise. Everyone has different genetic potential. Some athletes benefit from better training infrastructure and funding, better access to PEDs, greater political/social stability at home. With that in mind, I'd say get more data and - as the authors of the study say - find out where and how advantages exist and going sport by sport, try to make the fairest possible compromise.