I've been living in Chenggong since August.
The air is clean, roads aren't jammed up with cars and there are lots of parks to wander around. There are a couple of ok bars near the Qi Cai Yunnan mall and a few decent Dai, noodle and sushi places.
There's nothing here like Sals or O'Reilly's. You can jump on the metro and be in Kunming in 45 minutes.
Unitown is about 5km down the road with lots of bars and restaurants. There's only one "expat" style bar there...."Fiona's bar"
We have a popular Hash group in Chenggong and meet up once a month to walk on trails in the area.
You can check out our video here: youtu.be/eyFBumpYVlg
PM me if you want any more details.