My 0,02 euros.
My 2 cnt. Read with caution, this is just IMO, I have no deeper knowledge, and MIT is kind of new concept to me. Below is two cases that how I might work. If I'd use MIT, I'd probably do as case 1. For me, MIT would be next actions.
Case 1: Decide 3 MIT per context, And when you are in context, do those first. After done with then, consider changing context to do other MIT if appropriate, or continue with list doing normal next actions.
Case 2: Decide 3 MIT. At the beginning of day, do those three actions, in most appropriate order, changing context as needed. After MITs are done, continue doing next actions from current context.
Anyway, doing would not stop when MITs are done.
Generally I get the satisfaction when I mark actions done, after doing them. Anyway, very much of my doing actually don't come from my next actions lists. Doing work as it appears often is the most important thing to do.
Total GTD newbie, better with the GTD theory than implementation.