quick answer, which is what I do here, but doesn’t add anything not already discussed in detail above…
- add wired ethernet wherever you can; consider coloured cable, flat cable, cable in trunking, underfloor cable, out and around the outside of the house and back in again, anything you can do to get the cable there in the face of resistance from other halves, etc
— get as much wiring in as you can, and then, only then… - add mesh points where you can’t get wires, and for wifi-only devices like phones, gadgets. I strongly recommend ASUS Zenwifi, if you like having control, with lots of options. But see point 1.