I intend to buy a 3-pack Deco XE75 Pro to extend the range of my Bell GigaHub, most particularly into the back yard where it currently dies.  My Giga Hub serves a well-populated smart home of currently 20-25 devices, which (for historical reasons) populate a set of mostly fixed (but also some dynamic) IP addresses in the range 192.168.2.X.  Again, for reasons I don't want to get into here, I don't want to have to change those IP addresses.  I know enough about networking to sound as though I ought to know a lot more, but in fact I don't, and I am at this point totally confused about the precise sequence of steps I have to follow to install a 3-pack Deco XE75 Pro in my home setup.

Ideally, I'd use the XE75 as a WiFi range extender, but I have come to the conclusion that it doesn't work that way, and I will have to either (i) turn off the WiFi on my Bell Giga Hub, or else (ii) have it operate with a different SSID/password, and serve a different set of IP addresses.  [Question:  If option (ii), and the GigaHub serves IP addresses 192.168.1.X with its own SSID/password, will devices that connect to one of those networks be able to communicate with the devices connected to the other?]

Can someone please walk me through the optimum installation/setup sequence?  I'm very concerned that I might do something that I will find myself unable to recover from!