van Riebeeck said:
Ogryns, Squats... various other weird and wonderful variations of humans popped up due to environmental effects, which is slightly unrealistic considering the rate of human evolutionary process, but its a big galaxy further complicated by weird magical warp stuff, which is the unknown variable in the equation. As for co-existant homo sapiens, up until 24,500 years ago there where still neanderthals running around some parts of Europe.
As for the physical advantages/disadvantages of the sexes, it really is so negligable and highly variable across a population not to be worth the while to differentiate. I've known women communications riggers and rock climbers that have all the upper body strength, stamina and coordination that their male counterparts have, which is a trained and exercised part of physical development.