I scouted the area by car last year with an eye to doing a bike tour later. The two routes I checked may not be suitable for credit card touring as accommodations and towns tend to be far apart. But I saw good camping possibilities along the way.

The route that starts just east of Taddousac and heads north-west toward Sainte-Rose-du-Nord was very lush and very hilly. The road takes you right up to the fjord at times. I did not get as far north as Lac St Jean, so cannot comment. I have heard, however, that there is a bike route around the Lake, and that riding is good. On the way back to the St. Lawrence River, I passed through La Baie, and south-east through Saguenay Park, which was stunning.

So if you are happy to camp, travel long distances between towns, and tackle steep hills, it would be fantastic!