RBK 752 Guest Network question and general information

My 5 1/2 year old R7800 and Ex8000 combo having router issue lately (disconnecting connections and forcing password change when logging into it)and I picked up a rbk752 last night. I read manuals online but could not get my answers clearly before I open it. I work remote several days so performance is a concern.
1) the guest network does it transmit from satellite as well the router? Or just the router? Yes.
2) does guest network use same channels as main network? Yes. 
3) does the satellite broadcast on same channels as router (ex8000 is a different class and allows this as well as unique names on extended for guest network). Yes.
Lastly can I expect same coverage in 2400 sf home with Orbi? Currently router is one 1st level exterior wall and extender was in a room off kitchen. 25 to 30 ft away. Also have basement and second floor. Basement is unfinished and not included in square footage. Yes. 
The reason is I have some devices like humidifier/ thermostat/ sleep number that run exclusively on 2.4 and I created up a guest network in 2.4 ghz network for these that was outside of existing mesh. I had a heck of time with sleep number bed connecting previously.
New version v7.x FW has support for a separate IoT Nework SSID that you can configure for all of your IoT devices. 2.4Ghz or 5Ghz. https://community.netgear.com/t5/Orbi-WIFI-6-AX-AND-Wi-Fi-6E-AXE/New-RBR750-RBS750-Firmware-Version-7-2-6-21-Released/td-p/2333937/jump-to/first-unread-message