I haven't yet implemented these plugins into my unraid box, but it sounds like I am going to attempt what you are trying to do. Hearing that both server and client can't work at the same time isn't promising.
My goal is to have my unraid system download torrents behind a PIA VPN, and at the same time allow me to VPN in via my Android phone/tablet. For those with more experience with openvpn and unraid, is it possible to use the docker from binhex called delugeVPN, and the openvpn server plugin simultaneously? That sounds like the ideal situation to me.