Cloud saves are a feature that you get with your Nintendo Switch Online subscription, however, the compatibility of this feature depends on the game. For example, an E3 2019 interview that French site Gamekult held with Animal Crossing: New Horizons director Aya Kyogoku and producer Higashi Nogami discussed cloud saves.
According to Nogami, “New Horizons will not be compatible with cloud backups to avoid manipulating time, which remains one of the founding concepts of the series”. The interview also talked about the inclusion of the Amiibo. Kyogoku said that “given the number of cards and figures available, we think New Horizons will be compatible with Amiibo, but I cannot tell you more about this compatibility at this stage of development”.