Scenario 1:I was wondering - if we leave Canada now will we be able to come back with Valid Work permit and multi entry visa?
COPR issued while outside Canada. Your WP will expire automatically but you were not resident of Canada at that moment so you will have to inform them. They will reverse the PR decision temporarily and will validate WP back and you can travel back. You will be asked to inform them, on provided email address, when you land Canada again so that they can reissue new COPR
Scenario 2:
Before issuing COPR they will confirm your address and UCI or maybe first entry date to Canada. This will be a sort of hint that COPR is close. You can choose to travel back within some days and then reply them. Or right away tell them you are traveling. They will inform you further what to do. Probably the same thing "Inform us when you return"
Basically COPR is valid when they are sure that you were in Canada when PR was approved.
Travel on your Work Permit as long as its valid and you have TRV. If PR is issued IRCC will advise accordingly.
This is what I gather from calling agents.