I don't know about the microscale. There is variation in muscle tissue, such as "fast twitch" vs "slow twitch" fibres, but I don't know of any studies correlating (or not) such variation with sex.

Men on average have more muscle mass and lower body fat percentage. As well as that there is a difference in muscle distribution. Compared to women, men have a significant advantage in upper body strength but a more modest advantage in lower body strength. I've seen varying figures from different sources but the difference clearly exists. Upper body strength is important for punching, throwing objects, and wielding weapons - all abilities required to fight and to hunt.

Even if they're the same height and weight and have the same skill and general fitness, that upper body strength gives the man an advantage in a fight, which is likely to be one reason why combat sports usually separate men and women in competition even though they also have weight classes.