SSC and RRB exams have some difference. SSC have more complicated mathematics where as RRB has pretty easier questions. RRB focuses on a different set of Reasoning where as SSC have different kinds of it.

I would say if you want to prepare for both you can easily do that and for that I would recommend you to join a mock series which offers mocks for both kind of exams. You can go for Gradeup or Testbook for such exams. From their you will get the basic idea of the question and just go on building your knowledge from the books considering a basic idea from the question patterns.

I hope my answer helps. All the very best for your future endeavors!