In our old, long and narrow house I was constantly fiddling with WiFi extenders and in the end the only thing that worked acceptably was a Powerline WiFi adapter, but then I always had to make choices because Spotify and a Skype meeting at the same time caused misery .
We moved to a new apartment and during the construction I had two UTP cables installed in the ceiling; 1 in the living room and 1 in the study. The NanoHD in the living room and the AC-PRO in the study are connected to the UniFi Switch 8-60W (PoE) and the UniFi CloudKey (first generation) saves the configuration. The access points weigh nothing but to mount them to the concrete ceiling you need a good concrete drill and the plastic mounting plate is really just a flubber thing. But when it all hangs it really is a picture!
Thanks to Youtube I had prepared myself well and because of that I had it all up and running within half an hour. I was able to set the access points in such a way that there is little overlap between the access points. I see through the Unifi console that our iPhones, iPads and laptops have no trouble roaming when you walk through the apartment. A stable and fast connection everywhere in the apartment.
It costs something, but then you actually have something that works.