China is not one trip. It is a civilization that happens to have excellent trains. Beijing's hutongs and palaces, Shanghai's Bund and dumpling houses, Xi'an's terracotta army, the karst river at Guilin, and Chengdu's teahouses and pandas can each eat a week. The high-speed rail network makes linking them feel almost unfair.
The country runs on apps you may not have used before. WeChat and Alipay are how you pay, ride and talk; Google, Instagram and WhatsApp are blocked on local networks. That sounds harder than it is. Set the apps up before you fly, keep a VPN if you need your usual tools, and China becomes startlingly smooth.
Food is a reason to come by itself: Peking duck in Beijing, xiaolongbao in Shanghai, hotpot in Sichuan, and a breakfast youtiao that costs coins. Follow the queue, point at what looks good, and let the chili oil make decisions for you.
A first trip works as two or three cities on the rail spine — Beijing, Xi'an, Shanghai is the classic — rather than a heroic attempt to 'see China.' The country is too old and too large for that. Pick a thread and pull.