You can join the #netplay Discord channel here:https://discord.gg/JyW6ZgBUyS. This channel is for netplay discussion. There is also a bot that will announce new rooms when they are created.

Save files, cheats, and settings are synced from the player who creates the room (their save files and settings will be used for everyone).

You should test your controller in single-player/local mode before trying netplay. Make sure your controller works as expected for a single-player game.

Extreme input lag is usually caused by your computer not playing the game at full speed. If your computer can not play the game at full speed, you will "fall behind" the other player(s). You can try lowering the resolution setting if you have increased it.

No, gopher64 netplay is server-based. Don't let that discourage you, gopher64 netplay is not based on legacy technologies like Kaillera. It was written from scratch specifically for gopher64, and designed with input latency in mind.

No, because gopher64 netplay is server-based, there is no need to port forward.

gopher64 netplay manages input latency differently than legacy N64 netplay technologies. If someone has a high ping, only their input latency will be affected; it will not affect the latency of the other players.

No specific measurements have been done, but gopher64 netplay only sends key input data, not savestates or graphics, so bandwidth usage will be very low.

Yes, the server is open source, available here:https://github.com/gopher64/gopher64-netplay-server. When the server is running on a LAN, clients on the same LAN will be able to auto-discover it. The server will show up in the server browser on each client automatically.