Was thinking about playing though New Super Mario Bros Wii with a friend over netplay, will we be able to save our progress while doing so?
Also while I'm at it, the netplay guide says this about Wii games "Cache and Wii folders must be synced. ", I have no idea what that means.
Not sure about save files, but I think they will
As for the sync of Chace folder and Wii folder, in the Documents folder on your computer, in the Dolphin Emulator folder, the Chache folder and Wii folder must be identical for the both of you. So one of you will have to copy their folders and send it to the other friend, or you both need to start with a blank version of Dolphin
This is an advanced feature for capable users on GameCube games, which is much easier to handle. On Wii games, you have to be pretty much perfect in your setup or else it will end in failure.
As long as the Dolphin installs are 100% perfectly synced, I've never had issues with Wii saves.