Recommend a virtual lan software call "Zerotier".
Every player pc install zerotier and join the same network,and might need to set the metric value as "1".
And all player in the network will be able to access your server without expose to public network. (Either by ip or browse Lan network browser)
But this will not works for public access,as it will only show as Lan network,but public server list will not as no port forward set up.
I use this for my personal access to all device that didn't have public ip access.
And i also used it to play warcraft 3 with my cousin. (Old version that support LAN access,similar to Garena Lan)
To be clear,this software have very strong method for go through nat network,so normally 95% of device will establish direct connectivity to other device on the same network without going through their relay server. (normally no addition latency if direct connect)
I not sure if go through their relay server will get what quality of connectivity.But i think just add some latency only,since they might have singapore or tokyo server as relay.
Port forwarding is done at the main router. The switch doesn't have to worry about it. Latency will increase since the traffic has to physically travel further but it'll be in the hundreds or thousands of a millisecond.