I saw your stream about sweeping mines...... plus. I'm currently trying to get M on expert and master mode (ep.1). Some other MS+ content creator got M rank on both episodes, normal and master mode (except master mode ep. 2 expert).
no, M is the max you can get, it just takes more effort than S, think of it like a P rank if you've played pizza tower, gotta do it fast and dont get hit