I am completely against banning transgender girls and women from playing women's sports. 

I am a cis woman who has played sports since the 5th grade. I have regularly played against cis girls who were stronger than me, and I'm fairly strong - my body naturally produces more testosterone than the average female. Yet no one ever questioned my right to play (nor should they have).

As an adult, I play a full contact sport with and against transgender women. They are no more of a threat to me than the cis women I play with and against. 

Every body has advantages and disadvantages in sports - that's part of the game. You learn to play against people who are taller than you, more agile than you, faster than you, or stronger than you.

Every kid who has parents willing and able to pay for personal trainers has an advantage in their sport. The only reason to claim trans women have an unfair advantage and NOT declare that wealthy people have an unfair advantage is fear and bigotry. 

Trans women should be welcome in women's sports.