How can I route internet-bound traffic from our China-based sites to exit outside of China?

I am not your legal counsel, but if the traffic in question is not blocked by The Great Firewall it is fairly safe to assume that you are allowed to egress it via a PoP abroad for performance reasons. You should also consult Microsoft's documentation on the topic: https://learn.microsoft.com/en-us/microsoft-365/enterprise/microsoft-365-networking-china