Yeah. We all know that. No need to stress it. There is no such thing as bug-free rom. Even the official one is full of bugs. Minor translation bug, here and there, for me is not a big deal.
Like previous member replies, use plex vpn and choose shanghai. I did change to China dev rom before unlocking. It did work flawlessly. Don't know about stable china tho.
I don't think that's the case. TWRP have different data partition (data/media) something like that. So yes one need to format the data partition in order to use TWRP.