Sorry I haven't responded for a while, I have had a very busy work period. (As a TV freelancer you sometimes work many days in a row!)
mithrandi asked about posts, but as Kuhlkatz said, I would also have to hunt thru the forums to find the info. What I said about the road types and routing is how I understand things from reading many posts, as well as what I seem to experience while driving.
Specifically, driving from Somerset West to Cape Town (about 40-45km) I can stay on freeway type right into the city itself. And I agree with the typing based on the physical road itself. But a while ago there was a major accident which waze was aware of and was showing the heavy traffic, but insisted on routing on the freeway, even though there were many alternate routes that could (should) have been offered. Knowing the area I drove a different route which was definitely a lot quicker. I could see the traffic at a total standstill, yet waze keep trying to route back into the traffic.
Now, in this case I don't propose changing the type, but I use this to illustrate why I'm reasonably sure that road typing affects the routing. For a road going thru a town, leaving it as a Major Highway type when there are many stop streets or traffic lights might not seem a problem, but for those living there, waze might not work so well.
Searching for "routing road types" I found this in a French posting athttps://world.waze.com/forum/viewtopic.php?f=34&t=23408&p=248134&hilit=routing+road+types#p248120
0-15 km - All road types are allows for routing.
15-20 km - All road types except Streets.
20-30 km - All road types except Streets and Primary streets.
30-200 km - Only Minor, Major, and Freeways.
more than 200 km - only Freeways.
It seems to come from support but will take me bit longer to find. What it shows is that roadtyping most certainly affects the choice of roads used, depending on route length. It certainly would explain my experienced described above. I think the word "only" should actually be "only (when available)" otherwise it wouldn't find a route at all in some cases!
To answer chriseleven's question, my vote is a strong yes. I'm still not sure how to define the difference between Major and Minor highways, but I do think if it's an N road it should be a Major Highway when not a Freeway. Perhaps it could be dropped to a Minor Highway thru towns?. Thoughts on this?
Now I must get ready for another day's work - freelancers have unusual hours!