Is it possible to be both a rebel and a conformist?

or

neither a rebel nor a conformist?

Yes, I think so. One can rebel against a rule s/he doesn't like while conforming to something else. Your teacher may give you a homework assignment, but you rebel by not doing it because all your friends are going to see a movie and you want to conform to what they are doing and not be left out. You may demand that all people in America conform and speak only English at all times, and rebel when you hear a French tourist speaking French (or a recent immigrant speaking Mandarin to her husband, whose native language is also Mandarin). Lots of ways we can be rebels and conformists at the same time.