I'd like to know about VPNs and remote control of a laptop (for example I'd like to see if it's possible to control focus / exposure on a camera through a switcher connected to a laptop that I send out to client and then access remotely).
This is the modern thing everyone is doing. All your computers and devices on the same logical network even when they are remote. If you can control them locally, then you can control them remotely.
I didn't know I was looking for that but turns out I was too. Thanks. Should sort out the clunky collection of dynamic IP service and firewall rules that I've had sitting on my routers for the last decade+
What you are looking for is https://tailscale.com/
This is the modern thing everyone is doing. All your computers and devices on the same logical network even when they are remote. If you can control them locally, then you can control them remotely.