Have new online multiplayer modes been added to the classic games?

If the game originally had any kind of multiplayer features, those features will work online. Additionally, voice chat is supported for all classic NES and Super NES games via the Nintendo Switch Online smartphone app (available to Nintendo Account users aged 13+).

By using voice chat on the Nintendo Switch Online smartphone app, Nintendo Switch Online members will be able to enjoy these games together online as if they were sitting next to each other on the couch.