Think it Varies
Wasp:
I think it depends where in China you are flying.
I only did Hong Kong (quite a few times) and Shanghai (once). We practiced in the sim for recurrent using mm of Hg, and metric flight levels. Push the button, yes, but there was round-off error, as I recall, for setting the altitude window on the autopilot (which stayed in feet).
I believe we were told that it depended on the sector/FIR/UIR, and the more interior you went into the country, the more it became metric.
On the subject of accents: I was really surprised that the Shanghai controllers--who have really only been working with English for less than a decade---had far better English than the Japanese at the boundary hand-off----and they have been working with English since 1945.