Beijing, Xi'an and Shanghai: how much data
The classic first trip is Beijing with a day on the Great Wall, a high-speed train to Xi'an for the Terracotta Army, and then Shanghai. Ten to fourteen days of that means paying for most things by phone, opening a translator at every menu and checking train times, and it sits well in the 5 GB pack, which runs for 30 days.
The 3 GB pack lasts 15 days and covers a week in Shanghai with a day out to Suzhou or Hangzhou. If you add Chengdu and Guilin to the route, video-call home every night or film a lot on the Li River, take 10 GB. The 20 GB pack is for a month in China or for sharing with a laptop through the hotspot. The data calculator works it out for your own route, and all eSIM prices are on one page.