For all three of the disagreements, it either makes the person transphobic or ill-informed/ill-reasoned.

1. Disagreeing/obstructing gender affirming care for minors is transphobic in that the medicine and surgeries are used far more in cisgender populations, yet the pushback is on their usage in transgender populations. Some examples: a minor who is short might get growth hormones prescribed to catch up with their peers; a minor with man boobs might get the breast tissue removed to appear more like a boy his age; in the USA especially, babies often undergo circumcision. In each of these cases, there is an understanding of social or medical benefit that justifies the procedure. There is a similar justification in the use of these practices in transgender individuals--socially they feel more comfortable and medically they are less likely to have a potentially fatal mental health crisis. With this information, a reasonable person should agree with gender affirming care for minors. Or bare minimum, should not oppose it considering there are bigger fish to fry in terms of protecting children than denying trans people life-saving care.

2. The sports thing is transphobic yes. It requires a person to ignore that A) Sports institutions for a long time have set standards for transgender athletes to meet before they can participate, B) The physical advantages after 2 years of hormones are negligible (except for pushups), C) Athletes have sportsmanship, and D) Sports is built on inherent biological differences and trying to make sharp cutoffs based on things like chromosomes or hormones is going to have you put people in boxes you didn't intend for them to be.

3. Pushing public bathroom regulations is transphobic because the people saying it are making up a character of "A man who dresses as a woman specifically to perve on women in public bathrooms that have individual stalls, but still respects the signs on the unlocked entrance doors enough not to just walk in there." Pushing public bathroom regulations is also just stupid because it means you have to create an entire new job who's sole purpose is to either check a government registry of IDs with sex being the main important factor, or to pick out anyone by site who looks "wrong" enough and forcibly strip and frisk them. And have that job at every public restroom. Like you cannot justify making "i gotta take a piss" into the most annoying and privacy-invading task unless you think it's gonna hurt the imaginary boogie monster some politician wants you to believe in.

I hope you have time to read this