Get in touch with potential advisors, although I have no clue what my topic might be?
I don't think it is a good idea to contact them for several reasons. First, by your own admission, you do not know what you wish to focus on. Bear in mind your competitors probably already have a specific research question in hand. Second, even if you do have a research question at hand, academics in social sciences/humanities generally do not respond (of course, I can't speak for everyone) to potential candidates' emails prior to their official submission or consideration. That is to say, your prior email, in theory, has no effect on whether the professor would positively view your application that way.