Thank you cats_pajamas for the detailed feedback and the time you spend on this.

There are several ways to judge road importance: function, infrastructure and national classification. The regional and country specific pages we discussed above do clarify which one to use, as you rightly pointed out.

To follow decision made by the East Africa community and I can revert changes in ref tag I made (Rwanda, Burundi). I am not an expert in reversal procedure. But I can tag all roads currently tagged trunk in both countries, that are either not paved or not divided, into primary. Same apply for CAR. Do you agree on this, or have a better procedure to suggest?

For Congo, DRC, and other countries where no specific decision has been made, I want to point out that in https://wiki.openstreetmap.org/wiki/Key:highway it is written that "Note that highway=* distinguishes roads by function and importance rather by their physical characteristic and legal classification. Usually these things are highly correlated, but OSM is not obligated to copy official road classifications. " Which align with https://wiki.openstreetmap.org/wiki/Highway_Tag_Africa. 
So, I was wrong to give priority on the national classification rather than the function. And will fix this progressively (roads like RN9 in DRC you mentioned). But I am not sure I can consider the state of the road which is often variable along the way of single roads and can be labeled with surface=* and other tags. The RN6 you mention above in Congo is a good example. RN6 plus RN3 are indeed famously unpaved and 10m wide but do function as international link between Libreville and Pointe Noire. I have not taken this road so certainly someone who visited the place can tell more about that. It means to me that we should assess status based on the function of the road (connection between major cities) to remain consistent.

All the best