Each of the different sites has its own policies, rules, and regulations. The general essence of the Q&A, and some of the basic concepts like "spam is bad!", will carry over between sites, but not everything else. Things like how questions can be formatted properly, what is acceptable to the scope to avoid closure, and even how things are supposed to be tagged. You know how to properly tag questions on Stack Overflow, but this doesn't necessarily mean you know how to properly tag questions on TeX, LaTeX and Friends.
This is what the +100 bonus from account association embodies. It gives a user who has proven familiarity with the system the ability to have all the general abilities - upvoting, flagging, and commenting (formerly downvoting, but the bar was recently raised on that). But for the abilities in which their definitions do vary between the sites, like retagging and closing, it is important to participate in that community and learn about what rules that community has.
If you participated a lot in TeX and LaTeX questions on Stack Overflow, I believe there has been some motions to move questions over there. All of your earnings in those questions, then, would transfer if they got migrated. But even given that, I still recommend spending some time to learn about that community and its rules.