As you know iCloud run their services in different countries/regions.
I know nothing about other stuff on iCloud such as drive, but you should not use a iCloud email account from China region.
This is because, after my test, messages from iCloud China were just sent from a China server, which is in Guangdong Unicom.
184.108.40.206.IN-ADDR.ARPA. 3600 IN PTR cu-gy11p00im-quki07202302.gy.silu.net.
Due to the strict internet censorship from China gov, your privacy is not guaranteed.
And you should read the related articles carefully when you use an account from iCloud China.