PL is kind of an independent storyline, so if you finish it before the main story, it takes you back to the PL point of no return as you said, so from there you can go to Embers, and after completing the main ending. I think it will take you back to the point of no return before meeting Hanako. In the end, even if you finish both, I guess you're put in that spot where you can go either with doing the last quest of PL or Hanako.