Here is another source:
http://www.routeverte.com/ang/index.lasso

and
http://www.routeverte.com/ang/voyage...&code=saguenay
on the Véloroute specifically.

It's almost all paved now.

I didn't do it but many friends have. The bike-path parts are nice too so you may want to stick to it, unless you come with a road bike and want to stay away from the gravel. It's quite pretty.

The Saguenay region tends to be colder than southern Québec in the Summer (think 20-25 more than 25-30 - Celcius of course) so plan accordingly, for cold starts in the morning especially.

A few hills but lots of flats.

Just be careful if you drive up to there. The road is better than it was but still treacherous, especially at night (lots of wildlife running around). There is a way to cycle up but not on the main road that starts from Québec city. It's a nice ride, but a very difficult one (think HILLS for 300 km).

Maybe you should also look into:
http://www.velo.qc.ca/voyages/index_e.lasso
and make sure you check out the Grand Tour. It's a different kind of adventure, but a wonderful one. I'll be there this Summer.

Cheers!