you can split your wifi into 2 networks, 2.4Ghz and 5Ghz, you will find that the 2.4Ghz network has more strength whilst the 5ghz network faster speed.
So you should start with that and stress test it before adding wireless extenders.
If you have devices with ethernet ports don't use them wifi unless you have to and never use network over mains adapters, they are junk, they suffer interference from any transformer connected to the mains circuit and the latest 50Hz that mains power carries.
Run an ethernet cable network to each room of your house and use a link sys or Rasperry Pi wifi extender where you really need extra signal for wifi