We recommend an international e-SIM, such as the Airalo app. There, you can buy data volumes for regions or individual countries.
It is rather cumbersome to buy a SIM card locally due to the registration process.
Please note that almost all Western apps are blocked in China. This includes Google, WhatsApp, Facebook, Instagram, etc. This can limit communication. Those who purchase a roaming package from their provider before starting the trip can bypass the blockade, and all services can be used. For comparison: those using airport or hotel Wi-Fi cannot access these services. We inform about this because we want to avoid communication problems, especially upon arrival.