Be aware that you may be denied entry into the US under your TN status as the IR-1/CR-1 interview constitutes evidence of immigrant intent that may conflict with the non-immigrant intent requirement of the TN status. Unless you're placed in extended Administrative Processing, you have to plan to stay in Canada for a few days until the passport with your visa catches up with you. To lessen the chances of going into Administrative Processing, book the earliest medical appointment you can get once you get your interview date, and make a day-trip to Canada out of it. I don't think they deliver the passport to a hotel, either, so you might want to look at staying with family/relative/friend/etc. living in Canada.
You can fly domestically in Canada with a Nexus card or a Real ID-compliant or enhanced US driver's license.
