My few excursions on CA have been on very busy flights (though obviously I'm only peering backwards). Some Chinese government owned / backed organisations mandate travel on local airlines. Part of the answer to this is to:
- travel mid week, they are often quieter
- be conscious of the Chinese holiday cycle and avoid if possible. It operates off a different logic, and indeed calendar, than the West.

I suspect the flights to Chengdu will be a bit quiet to begin with, if the direct flight rule is negotiable. Also it's often cheaper to fly to HKG due to the sheer scale of competition on that route. Also if flying via Milan (etc) CW fares to HKG are quite reasonable.