It affects a little, but not to a great extent, I think. Due to the presence of the Y chromossome, a transgirl will get some unavoidable skeletal masculinization, and her hands and feet will be, on average, larger than that of XX women, and the same happens to height. A transgirl will turn out to be, on average, significantly shorter than the average male but still taller than the average woman. The same happens to XY women who have androgen insensitivity syndrome, their bones also masculinize to some degree. However, obviously someone who starts earlier will have better results than those who start post-puberty.