What is the China Currency Called:
Renminbi (RMB) is the official name of the currency introduced by the Communist People's Republic of China at the time of its foundation in 1949. It means "the people's currency". "Yuan" (CNY) ¥ is the name of a unit of the renminbi currency.

One quora post said,
The best (or at least how I do it) is doing it through a Chinese bank (ICBC, BOC, etc). It is usually free or at least much cheaper getting it at an international airport (Don't exchange at an American airport, just don't)."
Another said,
"It is better to exchange RMB into USD China. China clears huge volume USD, where as the US clears very little RMB therefore their exchange “spread” will be greater."

At 8 Best Ways to Exchange USD/RMB in China they say,

Where	Rates	fees	Disadvantages
Banks downtown (BOC and ICBC are best)	Best	none	eed paperwork and waiting time.
ATM with Credit/Debit Card	Average	yes
Small stores	Fare		Wach out for fake money
Airport	Bad	yes	Lines
Foreign Currency Exchanging Machine - XDM	Bad		Only at a few airports
Individual Money Changers	Usually Good		Wach out for fake money

My experience at Travelex at the airport:
Current exchange rate is 6.53 (Yuans/$) they gave 5.53 (85% of the market rate) plus a $10 service charge. Total cost $18 for 300 yuan ($46)(40%)