You can download the Famicom versions of Switch Online’s NES games from the Japanese eShop using a fake Japanese Nintendo Account. There aren’t many differences in most cases but it’s still pretty neat. Plus the Famicom box art is way cooler, and in the future Japan might get different games.
PSA: Switch Online doesn’t create backup saves for games automatically. You have to manually initiate the process by either loading the game or going into its settings by hovering over top of its icon and clicking “+”. Only afterward doing that will the backup saves stay updated automatically.