Apple is not doing poorly in China by any economic measure, but ya they don't sell many $200 Xiaomi/Huawei phones. I'm sure that Apple wins consistently based on phone sales revenue, even if they trail in total units sold.
The fact it's moving servers to China is most likely going to have positive effect on their sales, not negative.
The effect of iCloud moving will be mostly neutral. As long as WeChat continues to work on iPhone, whatever iCloud does won’t be very significant. I doubt most iPhone users in china even know what iCloud is.
apple devices are a few times more expensive than say Xiaomi, they thus stay in people's pocket for much longer. for shipment data, Apple's figure is not that fancy any more, they count for only 8% of the shipment in Q2 2017.
http://www.businessinsider.com/apple-and-samsung-are-losing-...
https://www.gartner.com/newsroom/id/3859963
Before start to waste your time, the 8% shipment in China figure was >14% just 24 months ago.
https://www.theverge.com/2015/5/11/8584277/smartphone-shipme...
To give you some extra details - I live in downtown Shanghai, as of writing, several months after IPhone X's release, I have not even seen the IPhone X yet as not any single one of my families, friends or colleagues has switched to that.
You are not the only one with this observation as well. Most of my friends and colleagues in different area of China had the same observation as well. I wonder why.