I usually use third-party apps for train tickets in China because I assumed 12306 was still painful for foreign users, but several friends told me it has improved a lot. If that is true, I would rather use the official app directly and avoid extra service fees.
For recent travelers, how smooth is the full process now with a foreign passport and overseas bank card? I am especially curious about identity verification, ticket changes, and whether station staff can easily see the booking if something goes wrong.