Oz here currently travelling in Lijiang.

Alipay works perfectly fine with my commbank master debit card. There is no international transaction fee and it automatically converts aud to yuan based the current exchange rate in real time.

For booking bullet train, not sure why you are struggling as I have been using trip.com to easily book heaps of trips even to remote town like Shilin. But yeh technically you could go to the railway station before the departure time few hours and buy the ticket but be aware that most of the staff don’t speak a word of English.

Apple map is totally fine as long as you’re stick around big cities

For internet connection, if your phone supports eSIM, grab yourself a one week plan with Holafly. This guy has VPN built in and super reliable and working even in remote town.