1 first of all, not all majors have masters and masters. Mathematics majors are all masters, and the related masters are only masters in education, that is, subject teaching (mathematics).

2. If you are quite a teacher, it is recommended to apply for a master's degree. After all, it focuses on teaching practice. Of course, it is also possible to apply for mathematics courses and teaching theory.

It's hard to say which job is good, because the competition for employment is fierce now, and the key depends on your own opportunities and abilities.