AdThen7403
Depending on your maximun distance from the Basement to the Second Floor if it is less then 100meters, you could backhall all cables to the main switch meaning all devices will get 1GB uplink back to the main switch and save on electricity and cost.
Not sure why you can't keep all Equipment on the Main floor where it will in the centre and 1 switch will work better.
As you were hitting nearly 900Mbps it maybe a glich on your end or the ISP, how is the speed also always run the speed on multiple devices.
With some configurations you could use these as Access Points other then that rubbish.
I recenlty setup this AP for a large Care home and turns our to be a good AP with decent price like £80.
https://www.amazon.co.uk/ZyXEL-Wireless-802-11ax-Manageable-Standalone/dp/B09925PHCZ/ref=sr_1_11?crid=37PDT72IY2V9H&keywords=wifi+6+access+ceiling+mount+ap&qid=1695826066&sprefix=wifi+6+access+ceilling+mount+ap%2Caps%2C513&sr=8-11
It is about right I think they say about 70% to 80% unless your ISP says you should get 600 then it will be a call to them.
If possible to run a cable you can always add an AP closeer to the Coop or if that's not possibel you can always look in for a WIFI extender. I am using this and works great.
netgear Extender EX7000
If you can run ethernet cable somewhere in the middle of your house then I recently setup Zyxel at onr of our large Care home which was having very bad signals with BT router.
This AP comes with alot of goodies specially the web portal, you can have multiple SSIDs with SSID schedule which is good if you have kids etc.
Thanks
On a connected device check the IP detail to determain your Default gateway and login to your router and see what is going on.
Also once you know your IP range i.e. 192.168.1.0/24 or depends what is your router distributing you can always put a static IP on a laptop and see if you can connect to the router, ping the router and go to the Internet.
Maybe somehow your DHCP pool is full not sure need to check this on your router.
Thanks
I have setup these APs recently and well worth the money and coverage is great with good features.
Zyxel Cloud WiFi6 AX1800 Wireless Access Point (802.11ax Dual Band), 1,77Gbps, Nebula APP/Cloud or Standalone, Up to 4 Separate WiFi Networks, PoE, Power Adaper Incl. [NWA50AX] https://amzn.eu/d/gBAJnJ5
Probably issue is with your WIFI card, get a usb WIFI adapter and test on the PC and see if you are getting better speed.
Also how is the speed from the LAN port of the PC?
Thanks
I would consider running a cable to an Access Point to an appropriate location. I recenlty installed a Zyxel AP for a large Care home and with one AP in the centre of the building they are getting good sigals around the house.
https://www.amazon.co.uk/ZyXEL-Wireless-802-11ax-Manageable-Standalone/dp/B09925PHCZ/ref=sr_1_11?crid=37PDT72IY2V9H&keywords=wifi+6+access+ceiling+mount+ap&qid=1695826066&sprefix=wifi+6+access+ceilling+mount+ap%2Caps%2C513&sr=8-11