I have a 4 story home . My quantum router is in the basement supporting my 3 boys in the boy cave. I installed a extender off my TV in the kitchen and another one in my 4th floor office. The connectivity to my nest camaras on the out side of my home are spotty . I shut off all the 5g for now concerned about interfearance. For sine reason I have poor connectivity on the main floor but the rest of the houses smart devices function with out issue. How can I improve coverage.
If you have an android device, download an app call wifi analyzer.
If you help you determine if you have signal strength issues or other interference.
If your boys are not connecting to Fios by Ethernet why keep the router in the basement. You could move the router to the 1st floor and put the extenders in the basement & upper floors. WiFi signals curve downward. The higher the transmitter the better.
Also: 5G always has less interfearance than 2.4g, don't know why you would turn it off.