As you know, you can't get PR card without completing landing procedure. So, your passport with “one-time entry PR visa” and Confirmation of Permanent Residence are the most important documentation when you come back Canada to become a permanent resident.
If you have become a PR at somewhere (US/Canada border) before your trip to home then either PR card or Permanent Resident Travel Document is required to re-enter Canada since you will not be permitted to board commercial carrier (airplane, bus, train, etc.) with expired PR visa.
This is my understanding.
Hope this helps.