I have some info.
A few years back (2017) I wanted to do the Transcanada but stopped in Kapuskasing and went back home for some reasons.
Anyhow:
I started in Sept Iles, then hwy 138 and hwy 172 to Saguenay. Then from Saguenay to Chapais on 167 and 113. Then Amos, Matheson, Cochrane and Kapuskasing. There was no dirt at all. The longest stretch without services was north of Sagunay to Chapais which was 225 km which I managed to do in 1 day. I saw 1 bear on that stretch straight on the road.
I left mid July and for most of the time it was never really t shirt weather - I was wearing a thin jacket almost all the time. I could certainly feel there's a big difference between the transam and this route which is much further north. I recall having 1 day where it just poured down for like 6-7 hours.
At no time I felt unsafe due to traffic. Of course there were trucks but they were not a problem even on the stretch from Matheson to Kapuskasing. I cannot imagine there should be MORE traffic going west of Kapuskasing towards Thunder Bay - unless there are some crazy big mines I don't know of. During trips like these I am more worried about finding services, food, a safe place to sleep and stuff like that.
The most beautiful scenery was between junction 138/172 and Saguenay.
Just ask if you have more questions :-)
Lucas