I shall comment on the height of the installed WiFi units. My experience is that the optimal distance from the floor is just over head height when standing. Say about 6.5 feet above the floor.

At this altitude there is generally very little furniture, people mass, etc so the signal tends to propagate well across rooms and through doorways. A surprising amount of WiFi signal strength tends to reach through the open doors, open room spaces and hallways. When signal has to travel right through solid walls and floors, it easily weakens.

WiFi signals do not travel well through multiple layers of structural materials, and especially poorly at shallow angles (where the signal is travelling through the length of the wall). Locate the WiFi modules so most of the portable device use locations have reasonable to minimal layers of building material to penetrate.