When you're running multiple, in the cleanest scenario, do you share devices back and forth between all hubs and keep all your rules on one hub? Or have relevant rules on each hub?
I've currently got zwave/zigbee devices and only official apps on my main hub then I use a second hub for IP connected devices and community apps.
I'm feeling like I should centralise all my rules for cleanliness.
My 3 hubs are divided into 'Zwave area 1' (aka Downstairs) and 'Zwave area 2' (aka Downstairs) with everything each hub needs for reacting to events. In other words: cause and effect. Cause is a Door Sensor or a Motion Detector detecting, which lets RM decide what to do about it, which is the Effect. Perhaps turn on a light, maybe more, maybe make an announcement plus send a Pushover notification. I put all Causes and all Effects plus the 'glue between' (RM in my case, but others like Simple or Motion Lighting) and nothing else. Because I have a dozen or so Pico's which are a 'Cause' then the Lutron Integration is on the Hub as well.
All the rest of what I want for a full system is on a third hub that would contain what might be 'risky Apps or Drivers' such as ChromeCast or Weather or Amazon Echo, even a WiFi Thermostat. It's also the 'coordination' hub for Dashboard, Homebridge, etc. In other words, almost anything where the Cause is out on the Internet and the Effect is simply some virtual switch.
This is ONE possible scenario of many. I don't think any way is specifically wrong. Each design will be solving some portion of the whole problem better than other facets. Mine solves the portion of the problem that has to do with responsiveness. For me, a responsive set of ZDevices is most important. I want to enter a room and not stub my toe on kid stuff, especially furniture moved for the purpose of a Fort. I don't care if the Dashboard is millisecond accurate. It's default 2 seconds of refresh is good enough. Therefore, mirroring the ZDevices to 'coordinator' as well as out to Dashboard and to Homebridge is not as critical for ME. Turns out HubConnect's so fast, it really doesn't matter.
That's my design too.. in fewer words. 
I have two hubs. At this point, both have both Zwave and Zigbee devices on them. I use different Zigbee channels but have no idea if that is necessary or helpful. The hubs are at opposite ends of the house, and devices are attached to whichever hub is nearest. This evolved when I got a second hub out of necessity. I originally only had a few devices and couldn't get a signal from the motion sensor over the garage to the hub in the back of the house. There is no good central location for me to place a hub.
When all the devices involved are on the same hub, the rules go on that hub. I use Hub Connect to share devices between the hubs as needed, and then put rules on whichever hub hosts most of the devices the rule requires. I suppose that could get confusing, but the majority of my devices are on the "back of house" hub, which I consider my main hub. My dashboards are all on the main hub.
I don't have many devices by the standards of some folks around here: 4 motion, 3 door, 8 or 9 switches, 5 outlets, 1 button, 1 door lock, 4 leak sensors [with 6 more eventually], a water main shut-off, and another leak sensor I'm only using for temperature. So almost 30 at the moment. (wow -- more than I would have guessed...). With some folks having well over 100, I can imagine more organization might be required.
It's Helpful.
Compare your home to an Apartment Building where your neighbor may also have a Home Automation system. In fact, in some apartments, you can have 4 neighbors each with their own smart home (cue hair on fire).
Trying to keep RF interference low is helpful. But you can't get too caught up in this because you can't control channel changes by your neighbor. In your case, that's you 
If you can keep them on disparate channels it helps in the physical overlap areas.
That's more or less what I figured. I've seen mention of trying to minimize interference with WiFi also, which leads me to ask: what is the correlation between Zigbee channels and WiFi channels? My nearest neighbor is a couple of hundred feet away and the only real interference I'm going to have is my own, so knowing how to minimize that might be helpful.
Here is a good chart that shows how wifi (2.4 GHz) over laps with ZigBee.
Read more here : ZigBee and WiFi Coexistence
Excellent -- thanks!
I have two hubs:
Hub-1:
All z-wave devices and about 20 zigbee devices that are not Xiaomi Aqara/Mijia compatible. This was my original hub and I use it to establish presence, mode, and HSM mode. Rules that use devices solely on this hub are run on this hub.
Hub-2:
The rest of my zigbee devices (contact/motion sensors, Aqara compatible repeaters, non-repeating bulbs). No z-wave devices. My Caseta integration is here. My cloud integrations are on this hub. Most of my automations run on this hub. Devices are exported to Hub-2 from Hub-1 using HubConnect.
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