When did you get P1 email? Do you have a valid work permit other or are you on maintained status waiting for BOWP?
From P1 to eCOPR (which is when you officially become a PR) you may wait 2+ months. If you're on maintained status, you run at the risk of loosing status, which may affect your PR application. I would just play it safe and pay the BOWP.
If you still have a valid work permit that's still valid for 2+ months, then you should be safe cancelling the BOWP application.