1. Pre COVID, IRCC would send the COPR by postal mail. Inland applicants had to either schedule an appointment at an inland IRCC office or visit the where the COPR would be stamped and validated. It would be as of the date of stamping that an applicant would become a PR. However, this has changed and now inland applicants receive the COPR by email and it is already validated, i.e. as soon as you get the COPR, you are in effect a PR as on the date of that email. If you are an outland applicant, you will get the PR, but it will be validated when you land in Canada and are admitted and the date will be entered on your COPR.
2. Are your form a visa exempt country? If you are then you won't need a PR visa. If you are not form a visa exempt country, you can still enter Canada via the land US border with your COPR and you won't need a PR visa. After you get your PRV validated, you will get your PR card in a few weeks and you can then use that when you travel between US - Canada.