you are trying to play with fire.
I had a similar situation when my work permit was valid, and then I had to travel for personal reasons from US to Canada, while awaiting my CoPR.
To keep things simple, better to postpone travel if you can. If it’s unavoidable, an immigration attorney is the best person to answer these queries.
In your case, you haven;t received your COPR. so you are technically on an active work permit.
If COPR comes, while you are in US, or if your plans are made, you can always explain that the plans were made while you were not a PR, and had not officially recieved PR.
One piece of information I got was that your work permit would be officially cancelled when you do your first landing as PR.
if you get CoPR before travel, (and assuming you get your landing appointment inland also before travel), then its simple.
If that doesn;t happen, when you come back from Us to Canada, they will take you in as PR, and cancel your work permit.
As I said, I had the same situation, but was able to postpone my travel to avoid such complexity.