It's a beautiful trip, but you're garanteed headwinds. I would go west to east. The wind blows from the southwest most of the time and can be very strong
along the St-Lawrence and in
Newfoundland. Cape Breton and Newfoundland are hilly.
I think a nicer route would be from Halifax, around the Cabot trail clockwise, all the way the west coast of Newfoundland, then across to Labrador where you can return to Rimouski on the
Relais Nordik (
Google Map). The boat ride isn't cheap and a bit long but it's a nice rest. There's a train between Montreal and Halifax so you can start/finish anywhere along that line. Newfoundland's west coast is quite flat north of Gros Morne and the wind really pushes you.
My trip around the gulf of St-Lawrence
Another trip in Newfoundland and Labrador