Hi,
I can’t answer your question as I’ve never used the addon.
But If I was your I used one or the other, either keep to using the addon or use openvpn via systemd.
openvpn with systemd allows for different configurations, using openvpn@.service.
To be honest if you going to change your vpn location and the addon works I just keep using that and not use the systemd setup.
Thanks Tom.