So I’m a VMware Horizon Customer / Engineer - I have a specific set of VMware Instant Clone VDIs that I created for a bunch of sales managers for the company I work for. They all use the iPad Pro 12.9s and they love them. They still need access to their green screen and spread sheets from a Windows VDI, so that’s what they have.
From what they report the experience is great. Make sure to use a keyboard with it and a Bluetooth mouse with it. Trust me, it’s worth it.
This VPN protocol usually uses a private key (client) / public key (server) combo that is used to connect through a public IP address (the 2 nodes can’t communicate it without) using the specified TCP or UDP (more often lately) and port to create the VPN tunnel that’s gets established during the handshakes.
There is a whole lot more going on with the process but that’s a high level view. But I have a WireGuard VPN service running on a raspberry pi that I put in a DMZ on my perimeter firewall.
But a port scanner would be able to see that port is open. Make sure you keep your software up to date. Hopefully the software devs of the VPN application is keeping their stuff up to date to avoid any vulnerabilities getting exposed in the code and a backdoor getting created because of it. As long as that doesn’t become an issue, no one will be able to get through without the private key. And those are usually uncrackable in a lifetime with the complexity and length of the key.