This article shows you how to turn off Wi-Fi on a Multy X(WSQ50). It can be used to only set up Guest WiFi or normal WiFi.
You can open Multy APP and go to "WiFi Settings" page, then tap "edit" (1.), disable WiFi (2.), and "Save" (3.) it.
Please note that Multy X is a WiFi System. If you turn off its WiFi, the whole WiFi System will stop broadcasting the set up WiFi Name (SSID). The WiFi can not be disabled for a single node.