I have a friend in China trying to use OpenVPN in China. But the app store in China does not have OpenVPN.
You create an Apple account, chose the region somewhere beside China.
btw, I don’t thing it would be a good idea to use OpenVPN to bypass GFW.
Most probably the connection will not establish even if you you set it up, because GFW will easily recognize openvpn footprints, but you can try with AmneziaVPN, it works a bit different 