I have not ridden across Canada, but I can say that the trail on PEI is pretty good. I rode some of it in 2019 (pre-covid)
There is no bike riding across the bridge from New Brunswick to PEI, a shuttle takes you and your bike across the bridge. And there is a ferry from PEI to Nova Scotia. I rode the ferry to the island, then later the shuttle across the bridge.
Most of my trip was on pavement, I rode the trail where it was convenient.
Bring repellant.