Hello @Eurochin
You can factory reset your existing Google WiFi units, set up a new network with a Nest WiFi Router unit, and add the old Google WiFi units as secondary access points to that new system. Whether this will actually improve your performance is a challenging question to answer. The Nest WiFi Router has an AC2200 4x4 radio that supports four simultaneous WiFi streams. Compare this to the AC1200 2x2 (two streams) radio in the older Google WiFi units, and it would appear on paper that it would be faster. However, those four streams would not be used to communicate with the Google WiFi access points via the mesh network, because the Google WiFi units only support two streams. Meanwhile, WiFi client devices could, in theory, take advantage of more streams, but only when they are connected directly to the primary Nest WiFi Router unit and only if they also have radios that support more than two streams. This latter requirement turns out to be somewhat rare. Some more expensive laptops may have three stream radios, but most phones, tablets, and gaming consoles typically only have two streams, and many fixed devices (smart speakers, "smart" TVs, etc.) may only have one stream radios.
So, with all of that as context, I think I'd try to understand what aspect of your existing system needs improved performance, and think about what changes could be made to address those concerns. For example, following optimal placement advice is the most important optimization you can make (current primary/router unit in the center of the home, secondary/point units no more than one or two rooms away from the primary in any direction – ensure they all get a "great" mesh test rating).
The other performance improvement that pays big dividends is using Ethernet as much as possible. Connecting an unmanaged Ethernet switch to the LAN port on your current Google WiFi primary/router unit will make ports available to connect nearby devices (computers, streaming video devices, consoles, printers), and enable running longer cables to more distant locations, where more inexpensive Ethernet switches can make ports available for similar devices in other parts of the house. Once this network is in place, you can connect your existing secondary/point Google WiFi units to this network, skipping the WiFi mesh interconnect entirely for the traffic from clients connected to that point.
If building out an Ethernet network like this isn't possible, you can still connect devices via Ethernet to the nearest secondary/point Google WiFi unit. This lets that traffic skip at least one wireless hop, improving performance.
In short, WiFi itself is a convenience technology – anything intensive should run over Ethernet as much as possible. But, some simple placement changes can still show improvements without spending money (and time) replacing your primary with a Nest WiFi Router unit.
