Automatically connect IoT devices to a VPN

So I have this GCP setup with IoT devices, but I want to SSH into devices that are geographically very far. Of course they are not on the same local network. My current idea is that I host a VPN and connect them through it while I am myself a client of this VPN. It works when I use a single device, however the autologin file (openvn.conf, user-locked) seems to only allow one connection and disconnect any other devices. Maybe I am misunderstanding how a VPN works, but how would one go about creating a new user automatically ? Is there anyway to have an autologin file that handles multiple devices ?

I am using OpenVPN Access Server v2.7.5 with a Debian Linux distribution on the devices.

Thanks in advance.