Review steps on adding a 2nd hub

I've recently moved and my GF has her own, fully operational hub (a c7). We don't do Zwave and never plan too.
Her home is 4 bedrooms in a sort of ranch style (read: long hall) way. I've repeaters in each room and zero problems.
I'd like to put my old c5 into the master bed (the farthest end of the house).
Some very basic questions:
2 hubs that will be meshed - both should be on same zigbee network. True?
I need to factory reset or can I just 'add my old unit as it is' without problem?
I use Mode Manager on the c7/main hub. Some documentation points out a gotcha on mode manager for added hubs - is this still true?
Do I need to push custom drivers I've made into both hubs, or is it only necessary to have the driver on the hub that is managing the device?

No, each hub has its own Zigbee network. Hub Mesh is just a way to share devices from one hub to the other over your LAN. It does not participate in or even care about the underlying protocols that the devices themselves use. (I know the name of the feature can be confusing; "mesh" here is more of an analogy, not anything related to the Z-Wave or Zigbee meshes.) There's also no way to join one hub to another hub's Zigbee network in the first place.

I'd recommend a soft reset plus a reset of the Zigbee (and Z-Wave if you ever used it) radios, but a "full reset" should not be necessary--this will basically do that.

The only thing I'm aware of is that if you have one hub configured to follow modes on the other, then you shouldn't install Mode Manager on that second hub. First, there's no need to--it will get the mode changes via Hub Mesh since that is what it's configured to do. But second, it could cause conflicts--Mode Manager on the second hub could change modes independently of the first if it's configured differently, and that's probably not what you want. (This isn't really Mode-Manager-specific, so I'd keep it in mind with any way you might change modes: pick a hub to do it, and just let the other follow if that's what you want.)

If there is some other documented "gotcha," I suggest providing a reference.

No, only the hub with the "real" device needs the custom driver.

The real question here is why does she have a new C7, and you get the C5 ? JK

Anyway, what I'd do(if the 2nd hub is even necessary) is pair the devices on the farside of the house to your C5. Place the C7 on the other end of the home and pair devices in that half of the house to the C7. Set the hubs zigbee channel so they don't overlap with each other. Also consider your wifi channel, as it may need to be changed based on the new RF pattern in the new location(15 neighbors-all using Wifi CH6), which in turn would dictate which zigbee channels to not use.(see threads on wifi/zigbee coexistence )

And if you've never used Hub Mesh, it's fantastic and makes having multiple hubs very simple.
Lastly turn off your Z-wave radios, no sense adding unnecessary RF into your home(wife looks at me with head titled). This from the guy with 6 hubs, 3 wifi satellites, 2 routers, 2 Rpi's, 12 Wyzecams)
but but I need all those


@bertabcd1234 @Rxich Thanks gents! - Good thing I asked about the zigbee channel! I really misunderstood that - I will seperate. Likely 15 and 20. I'm already on 20 for my zigbee.
I've read and believe I understand about the channels for WiFi as it pertains to zigbee / 2.4Ghz. I'll check with a wifi Analyzer app on the phone to get a quick overview of how active the band is and where optimum non-overlay is.
She got the c7 as a way to convince her it was worth paying for all this stuff!!!
Side Note: The GAF shot through the roof and I got pre-approved to purchase wall switches when I showed her the security camera images on the dashboard for a wall tablet .. Never under estimate what makes others feel safe!
@bertabcd1234 no - you understood it correctly - the reference to a gotcha was in my search for related strings I saw statements about being careful with Mode Manager being installed/enabled on downstream/secondary hubs.
It's my intent to offload custom apps onto the C5. I'll keep the c7 for built-in. Based on 2nd thoughts and the comments I may simple disable both z's on the c5 completely. I have a tad troubleshooting to do - as I've now had 2 'Your zigbee network has gone offline' issues - they never occurred on the c5 even though I had a much larger physical and node sized networks on it. But that's for another thread.
Thanks! Marked as solved.