From my Chinese trip last year did a variety of methods when needing local currency:
- ordered $AU300 worth of Chinese RMB (yuan) from Amex and picked up before departure, fairly painless and exchange rate ok.
- exchanging in a Chinese bank was a waste of an hour of my life, it was so slow and English language was a problem, even my chinese-speaking relatives had problems trying to get understood, supposedly simply to exchange money. Might have been different at a different bank - never took a photo of a sign from the "Evergrowing Bank" but should have, some of our banks should also be so brazen with their names!
- some hotels offer reasonable exchange rates and are fairly hassle-free, Shangri-La was a good experience
- ATMs are happy to accept your linked card and let you withdraw local cash, you get charged for it when you see your statement. Easily the most convenient way but more pricey. I think the machines warn you what they will charge you before you accept, but don't definitively remember
- did NOT try any streetside exchange places, was not recommended.
Probably not worth wasting too much time to get the best rate you possibly can, go for the easiest and quickest if not too costly. Exchange rate should be so good at the moment anyway, not worth haggling over small rate differences when there is plenty of other haggling to do when shopping in China!