How am I able to let my 2 PC over internet see one another as if they are on the same network segment?
With a VPN.
You have tons of options to choose from.
With a VPN. Usually in advanced routers you can setup one, this means both routers in both ends must support it.
If both ends have a computer you might leave them switched on, use it as a server and setup Openvpn there. the router then will just NAT the openvpn port to the server and from the server you will have your LAN plugged to your SWITCH who will connect your pc.
An application called teamviewer might help you too, there's a vpn option but I've never used