My house is setup with the nest router in the basement wired, and then a mesh point on the main level and an additional mesh point on the 2nd level. I have AT&T fiber coming into the house and consistently see speeds around 800 Mbps coming into the nest router. When I am connected to the nest router in my basement, I typically get wifi speeds around 400 Mbps. However, once I have moved into other parts of the house and connect to any of the mesh points, my speeds consistently drop to around 120 Mbps. I then tested unplugging all the points and discovered that if I only connect to the basement router I can typically get speeds around 300 Mbps. Why would connecting to the mesh points cause me to receive SLOWER speeds over connecting to the nest router directly?
There are a couple reasons for this, but the most important reason is that there is one 5GHz channel being used for both 5GHz WiFi clients and for the wireless mesh interconnect between mesh secondaries and the primary (router). So, any 5GHz client traffic will need to be sent over that channel twice when that client is connected to a mesh secondary, but only once when it is connected to the primary/router. What a mesh system like this does is essentially trade off peak performance in exchange for a larger reliable coverage area. You may find that you don't actually need the extra coverage in your home. If that's the case, then just use the primary/router by itself.
If you want to keep the secondary/mesh units in the system, though, you may be able to improve the performance of the system by ensuring the secondaries are close enough to the primary to get a strong 5GHz connection for the mesh interconnect – the guidance is no more than one or two rooms away (in any direction). They can then provide coverage to more distant clients from there. You should run a mesh test and make sure they are placed such that they all show a "great" mesh connection quality. If any of the units has a poor mesh connection, any time it spends talking to the primary will take 5GHz channel capacity away from all of the other demands on that channel.
I hope this helps.
So disconnected the Google mesh system and spun up a new gear orbi wifi6 setup and getting speeds at the router at 950 Mbps, and wifi speeds in excess of 600 Mbps throughout house. This really can't be a problem with location of points as the orbi point is essentially is in the exact same place. And I setup the wifi name and password exactly the same so most devices reconnected. Something must be up with the Google nest wifi devices to be performing this poorly compared to net gears devices thar are using the same internet in the same positions
@MichaelP, thanks for the help!
@tainted02, I'm sorry to hear that you had to replace your Google WiFi system. It's possible that your Orbi system is getting better speeds since it has Wi-Fi 6. You could click on this link to learn more about troubleshooting slow speeds with your Google Wi-Fi.