As long as you're in a private car, you can cross any land border with copr (must be signed and stamped- that's what makes you a PR). My sister and I went to the US twice with copr (and passport with US visa of course) before lockdown driving from Ontario to upstate NY and back with no issues.
Pr card or prtd are for public transportation company/airline personnel to verify your status. So you cannot use copr on greyhound, train, plane, etc.
vs land border, in a private car, you answer to no one until you present yourself to CBSA official who can verify your status. Hope that makes sense
I've also since got a job with copr and sin number.
https://www.cic.gc.ca/english/helpcentre/answer.asp?qnum=064&top=10