Complete and review one GMATClub Test per day so you can finish on time and still have two or three days to relax before the exam. If you are determined to attempt a 750 score, then these tests are essential.
I didn't do any OG questions until I completely finished the
MGMAT math books. I did the questions in order. In hindsight, this wasn't the best strategy for me. Go ahead and do the suggested problems. That way, if you have any trouble, then you know exactly which section to review in the
Manhattan books. It also helps to reinforce the concepts learned. Finish any remaining OG questions afterward.
But here's something very important: if you find that you are not comfortable with this, then by all means switch strategies and complete the questions in order. We're all different, and it's important to adjust our studies to our own style.