I was Moodle for two classes, with 700+ and 400+ students. We use Moodle quizzes in a similar way to what you ask.
We have non-graded, try as many times as you like, from anywhere "practice self assessments" which students use to help prepare of the graded, single attempt, in class and time limited (50 min) "assignments". They write 5 or 6 assignments across the semester. The structure of the two item types are similar (i.e. drawing from the same pools etc).
We also have the "final exam prep" and all I did there was create another quiz that selected questions randomly from all the pools in the whole course rather than the subsections that the other materials use. A good case for a good structure of your question database.
So we essentially use your option B and it has been working fine for us.