Different Wi-Fi routers support different radio modes, so the setting varies depending on the router.
Generally, we enable support for all modes. Then, the device can automatically select the fastest commonly supported mode for communication. Selecting a subset of available modes will prevent certain devices from connecting. For example, 802.11ac devices cannot connect to Wi-Fi routers in 802.11n only mode. In addition, selecting a subset of the available modes may interfere with old networks nearby, and old devices nearby may interfere with your network.
Source:
https://support.apple.com/en-us/HT202068