Hello,
Each Google Wifi point is a router that's designed to work with your existing ISP and modem. Google Wifi can create a mesh network only with Google Wifi and OnHub routers. Google Wifi will work with most connected wireless devices including tablets, printers, and smart appliances.
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A Google Nest Wi-Fi router can connect to an existing wireless router, but this is not recommended because it may cause issues with the wireless network's connections. ... The Nest Wi-Fi points must be connected to a Google or Nest Wi-Fi router; they cannot connect to a third-party router.
Cheers, J Wick