I can't answer your specific queries, but anywhere you go in China you should carry sufficient quantities of cash to pay for food and activities. Whilst credit cards are fine for hotels and larger restaurants, cash is king in China. Have plenty of RMB100 bills on you to pay for smaller things - and change larger notes at more "honest" places if possible.

Credit cards may be able to be used at certain places, but MC and Visa are more popular than Amex, so definitely don't rely on just an Amex.