FaceTime and iMessage work fine in China without VPN. For my customers in Europe and USA who have trouble with WeChat, iMessage and FaceTime are our fallback app.

WeChat, on the other hand, does not like non-Chinese IPs, speeds slow down. If I am using my VPN and someone calls (or worse yet, video calls) me on WeChat, I often have to turn off my VPN to get better internet speeds.

And when I'm in the US or Germany, on wifi, sending big files or videos by WeChat takes a long time. Still usable, just slow.