Most of the larger airports have one or two priority pass lounges you can use. They are usually not that good but depending on the airport they can be better than sitting by the gate.

Some airports have reasonable priced food for sale and others try to rip you off like they do in the US/EU.

Star gold in economy will always get access to Air China or Shenzhen Air lounge when flying domestically. ST elite plus won’t have access to MU lounges on purely domestic itinerary unless they are in Biz class.