"Regarding the HDD cage, where would be the optimal placement of the HDD/SSD that I have? In the portion where there is least air intake by the front fan (so that cool air would propagate more inside the case) or to the area where there is sufficient cool air intake by the front fan?"
It really doesn't much matter as far as airflow into the case because the HDD rack doesn't have wide enough openings to allow better flow if you didn't have any drives at all there. So I would suggest a similar setup as mine.
Sorry I would have gotten to this earlier but we're still dealing with a fire here. So far things are holding up fine for us.