I did Toronto to Quebec City, with a long detour - Kingston to Perth, Perth to Ottawa, Ottawa to Montreal. I was visiting friends along the way.
When I got to Montreal cyclists steered me to the many bike routes through the city.
I did 132 to Quebec City, then stayed at the hostel for a week, took the train back. But you could cross at Levis. When I drove to PEI, I would stop at Rivieres des Loups, and then go south into NB. You could continue on to Mont Joli and go south from there so you hit the coast of NB.
It isn't that risky a ride, Highway 2 is pretty flat. I recall a big hill between Trois Rivieres and Quebec City but not nearly as big as the hills between Ottawa and Montreal on the Quebec side of the river (Deux montagnes, Oka). Lots of small towns and farms between the big cities.