Form of study

I don't think there is a 'school answer' to this, meaning a correct answer. Certainly not the same answer for everyone, but not even a correct answer for a particular person. Of course, it also depends on whether you are striving for teaching Halacha or for scholarship. My personal position is that after you understand how the business works (and I assume that by the time you've reached ten years of kollel, you're probably already there), there's not much point in engaging in expertise, and it's better to study ayun. It's more useful and productive, and requires less repetition to retain it, and gives you no less expertise (actually more, because the study is more organized and its details are interconnected). In my opinion, midrashim and thought are a complete waste of time, and I wouldn't touch that.