Hi Jasper,
I haven't been outside China since I bought the iPhone 13 Pro Max, but here are some answers based on my experience, what I read, and a long talk on the phone with Apple Support.
1 and 2: It seems that the Chinese model (A2644) and the "Rest of the World" model (Model A2643), that is sold in Europe, support exactly the same 4G and 5G standards. This document suggests so: https://www.apple.com.cn/iphone/cellular/ (Chinese) or https://www.apple.com/iphone/cellular/ (English).
3: Yes, I can access the Dutch-App store with my Dutch Apple ID, both with and without VPN connection (without is often much faster). iOS updates download super fast without VPN. The sync from iPhone to iCloud, and vice versa, is however very slow with and without VPN..
The only thing that I really overlooked is that the much used ride-hailing app Didi is currently not available in any app-store due to the scrutiny of this company by the Chinese government. But that is not an issue related to the Chinese model, but rather an issue with the closed Apple system. On Android I could have copied the apk-file from my old phone.
While Didi is the only ride-hailing app with an English interface, there are alternatives in Chinese, such as MeiTuan and that works fine if you can read some Chinese; most addresses can be entered in PinYin which makes it easier to use.
4: According to Apple Support, the warranty, and extended warranty with Apple Care, is limited abroad, but only when it concerns parts that are different. The support staff even suggested that in case a complete replacement would be needed, you may end up with a model from a different region. This is very different from what they told me in the Apple Store here in China, where they claimed that outside China there would be no warranty.
Hope this helps.
