I’m pretty sure all humans have the same number of muscles in their legs. Some people are more muscular than others, and some will have more “fast twitch” fibres than others, making them potentially better sprinters, but there is not compelling evidence that people from certain parts of the world have more of these than other people.
the exact number of muscles in the body is difficult to state as exactly how you define and seperate different muscles is complicated and different people have different definitions. eg the biceps in your arm (as opposed to the one in your leg) has two two seperate attachment points…..so is that two seperate muscles or one ?
I did spend time in an anatomy lab in Brussels doing cadavar dissection to learn anatomy and in that lab they ‘discovered’ (defined) a muscle in the arm pit that not everybody has ! so not everyone has the same muscles…..but the differences are very small and dont affect sporting performance. The much more important difference is the way in which we train the muscles we do have.