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.

The only reason I can think it would be expensive is if it was a really complicated run. But seems way too much.

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.

Not really sure what you mean by “I have 20”. If you are concerned, doing a factory reset might solve the issue of there is something weird and someone was able to get into your network.

If you never update your router, you should probably start with that. Not using default passwords would also be smart.

TLDR: Clear out any QoS settings or factory reset. Update. Don’t use default passwords