A belated reply here too, I only just got a notification you’d replied 
With regards to the difficulties in identifying roads it’s mainly down to the way some of the areas seem to have a mix of dry riverbeds / streams, well-trodden paths and dirt roads, often through trees or taking several routes to get to the same point. To the local people in some of these places they may well be roads used by cars but at the same time they could easily be a road through an area of farmland that’s used by a tractor on a regular basis. There’s also the time-old issue of mapping from satellite images where you kind of think there must be a road between several buildings but trees are in the way so you might not get it 100% first time.
Because you only see your “challenge square” and a bit of the surrounding area you can’t always make a judgement based on the path of a road that’s more obvious.
At this point my focus is on the roads that are clearly taking people from one side of the map to the other as a bare minimum and then any connecting roads that appear to be well used and follow a strict path. It’s easy in some cases as they are obviously tarmac / asphalt but you just have to use your judgement. I think the important thing is to get the basics in place now to form the major routes, the detail and refinement can come later.
There’s no element of defining the types of roads at this point, for those of us testing at least, it’s just “here’s a road, it’s a line, it joins to this line” stuff. There isn’t really even the concept of junctions as far as I can tell, I presume Google will be able to work a lot of this out with GPS data and checking how objects interact with the roads or through recruiting local guides in these regions to help. One thing I have noted is that some people seem to be adding two roads running parallel to each other where there’s a major route with dirt between each side, I’m not doing this as I’m hoping at a later time you’ll be able to define the road by type and it will automatically map it like this.
I completely agree with you regarding the way the points are being handled, I like to see my own stats but don’t want to have them compared with others or have specific targets as this might encourage others to lower their standards in favour of just getting lines on the maps. There’s an approval phase but I don’t know if this has any human element to it. There’s some fairly low quality additions popping up but thankfully you can also modify other people’s lines if they haven’t been approved yet (I presume they aren’t approved anyway).
What’s nice is that when the roads are approved and added to maps you can see that people have already started to add places near to them or you’ve connected up some existing businesses so hopefully people can now navigate.
As you say it’s like Waze / MapMaker in that you see you’ve add XXXX km’s of road, in this case you get that broken down by number of “challenges” and per region as well as a guide to show how many days in row you’ve worked on it and how many meters or road you are adding per second.
It’s quite fun, pretty therapeutic and a great way to pass a bit of time, especially in these times when we aren’t supposed to be outside. Hopefully more people will be brought in soon.