If you have a router, let oss say the Asus RT-AC68U and that connects to a nother router Netgear R7000 behind this but in AP Mode with same SSID and same channel, Will this be seen as ONE unit by the clients and Switch over to them automatically then?
Won't be seen as "one unit", but it will be seen as a singular network...
Handovers from one AP to another - depends on clients, and AP spacing - there are conditions that some folks would consider clients as being "sticky" to an AP, but this goes to levels perhaps not being at the point to trigger the client to seek a better AP.
Thanks m8s, as long as you do not have to log on to different SSIDs in the apartment and as long it switches over to the router you are closest to, will be fine for me.
So same SSID, same channel or not, just try out or error on that one.