The OP means VPN client not VPN server.I'm no expert on this, but I am using Wireguard myself and I found it to be a fairly simple process to set up. You just need to switch it on and add a user. Then, you will be presented with two options; a QR code for mobile phones and an option to export the configuration file for computers. All you have to do then is download and install the Wireguard app on your devices and then either add a tunnel by scanning the QR code in the router's GUI or importing the configuration file if using a computer. OpenVPN is a bit more involved from what I remember, but if you click on the ? in the GUI, it will give you some links to help you set it up.
What do I need to set to make this work?
If you haven't seen it already, see the Asus-Merlin Wiki page for VPN-Director, which generally explains how that feature works. You will likely, if you haven't done so already, need to create a VPN Director "rule" to handle the clients.What do I need to set so that they don't both use OVPN for internert connection?
On the VPN Director page you can create rules, by selecting the local and remote IPs (these are optional, you can leave one of the fields empty to indicate "any IP"), as well as the destination (either WAN to bypass all VPN tunnels, or one of the five OpenVPN/WireGuard clients). You can also enter a short description to identify that rule on the web interface.
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