A lot of the 20/30 markers will need you to incorporate theories. You may get a question like "evaluate functionalist explanations of the role of education" and you may have something similar with crime "evaluate theoretical perspectives on crime". For gender differences in education, there are specific concepts and theorist so I don't think theoretical knowledge will be needed. In Crime, theory is very important e.g. a 30 marker on ethnicity and crime will require a lot of theory (Right Realism, Left Realism, Neo-Marxism etc.) along with the specific content.
I'm not sure what you mean by a 30 marker with gender and ethnic differences - do you mean a question that requires you to do a para on gender, then ethnicity, then class?
If so, I'm pretty sure this is possible. It could be something like "...evaluate sociological explanations of differences in educational achievement between social groups". I'd probably do a paragraph per social characteristic (I personally wouldn't do a fourth but there's no right way).