Hey french compatriot ^^
Me too I was in a big bullshit to play wow in china ^^
So here what I discovered:
You can play wow with a french version in China, the technic is written in the forum (look in te topic how to play, etc.) but to resume you just have to setup the french version until the 1.12.1 version and then just copy some files in the wow file.
Concerning private servers, if they are chinese I can't help you much
But if they are in french you will need to setup the french version (yeah I know that s**** but you need to setup 2 wow on your computer
I hope I coul answer a little bit, or another thing for your help if it takes too much time to setup, just do like me: