The use of the tag 'trunk' is China is mixed. Trunk properly means the national trunk network - i.e. the G-roads, that run between provinces The G roads that are motorways should be tagged - motorway Trunk does NOT mean dual carriageway, and it is not an indication of the importance to LOCAL traffic. It is more a function of length.
'Primary'is suited to Regional roads, the 'S'roads, since these make up the primary network in a province. 'Secondary'are the county roads.
For those mapping cities, rather than highways, the use of the tags is arbitary to indicate the local importance of a road. In this case you might choose to use the 'trunk'tag to indicate an important non-motorway ring road for example.