You could set up a vpn. They would need the cert on their side. So if you are allowing someone on the outside connecting in, there is always a chance. But it’s up to you. Sounds like you have it figured out and you just need to pull the trigger and do it
If the port is just labeled “WAN” then no. Unless you are talking about your router which is a different discussion. You are just talking about your local network. You are not talking about opening your internal network to the world.
I would recommend using something like truenas that supports iscsi. Sometimes games need to appear that they are installed locally and if you use something like that it will appear as a local device. Network drives are not great from my little experience.
Something else to consider is that some games “require” ssds so if you do not have a fast connection you might run into other issues.
1 NVME pcie 3.0 ssd will saturate a 1Gb easily. From my understanding and low math skills you would need a 10Gb connection to get this speeds from one drive. Factor in overhead for processing and networking and you should be fine. You can get cheap cards and switches for this.
If I remember right there is a Ubuntu arm version. Install the gui. Jeff geirling did a video on it with ampere
Ampere or snapdragon if they ever get the kahunas to try it. If framework did that I would loose it.
Smb is supported. So if you have two PCs that can see each other you can have permissions on folders that you want shared. It’s up to you.