[jrref]

A couple of comments:
1) From my experience either with new installs or helping fix installs that I'm not involved with, most techs will try and place the wifi device in the most central location as possible such as above the Kitchen cabinets or Living room and will set the network name and password to the existing one and try and get all the customers devices on-line. But the tech has only a certain amount of time to spend on the install so usually, when a customer has a lot of devices such as cameras, door bell, streamers, printers, etc, if any don't come back on-line, it's up to the customer to get that done. Some cameras and doorbells or smart switches will need to be re-installed even if you use the same network credentials and most techs will not have enough time to do all that work on your install. Forget about if the customer has multiple networks or some sort of complicated set-up. With every provider, Xfinity, Spectru, Quantum, etc., there will always be that "lazy" tech that will install the wifi device in the easiest location and hopes for a wifi signal all over the house. I can say with Quantum, I have not run across any "lazy" techs and they are reqired and do a wifi network survey after the installation to make sure you are getting "adequate" speeds all over your home or they can't close out the job.
2) I agree with a single wifi device it's difficult to get good coverage throughout your house. But if the wifi device is placed properly, I've seen very few houses here in the Villages where you couldn't get a good signal all over the home. This year I've helped 45 Villagers with their Quantum install and have a 100% sucess in getting a good wifi signal all over the home by placing the Quantum main wifi pod in the best location. I know that's not a large sample but it's large enough to make the point.
3) There is no way to get full speed wifi all over your home with a single device. Granted, if you have 100Mbs or 300Mbs, yes you can see that speed everywhere on a smaller home but you won't have that same result with 500Mbs or 1Gbs, or other faster speeds, especially with the upload speed. If you want full speed wifi all over your home you are going to have to need a mesh wifi or other equivalent system.