From everything I have read, yes, that creates potential for issues due to interference, especially if the two hubs are located nearby. Also, if you're now using channels 20 & 21 for Zigbee, your 2.4GHz WiFi should be set to channel 1 for the least interference. See my earlier post in this thread here (if you haven't read it yet.)
As for Aqara sensors vs original Xiaomi ones, I have a bunch of each of Door/Window Sensors and Temp/Humidity sensors, and haven't seen any trend for one type or the other dropping their connections.
My SmartThings hub, which is in the same centrally located room as my Hubitat and my 5GHz/2.4GHz WiFi router, is on channel 15, and I also never had any Xiaomi devices (original or Aqara) drop off.
Here's what I've tried for channels with my Hubitat Hub so far:
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Channel 26 - Most Xiaomi devices paired relatively easily, and out of 21, just a nearby Aqara Leak Sensor and a more distant original Xiaomi button lost their connection after 3-4 weeks. I did some reading on Zigbee & 2.4GHz WiFi interference, and after l checked the WiFi channels used by neighbors and read up on how my WiFi router handles its 2.4GHz high-speed mode (see my post here), I decided to change my WiFi 2.4GHz to channel 11 and my Hubitat to Zigbee channel 13.
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Channel 13 - I got impatient waiting for devices to "find" the new channel after changing it, so I sped up the process by manually re-joining them, which went quite smoothly. But then about a week later, when I was trying to re-join a couple of original Xiaomi buttons that I had temporarily moved over to my SmartThings hub for some DTH code testing, my Hubitat just wasn't "seeing" them.
I also wasn't able to pair a number of other Aqara buttons, including two of the brand new Aqara model WXKG12LM that I had been able to pair with the Hubitat just some days prior. I even tried temporarily changing to a number of other Zigbee channels to see if the devices would repair, but with no success. After another week, after Hubitat staff confirmed there hasn't been any changes in recent hub updates, and I also wasn't able to pair a Securifi Peanut Plug I bought, I decided to reset my ZigBee stick and start all over again.
Due to a glitch with manual Zigbee Channel selection not working correctly after the stick reset, I landed up on channel 20 (but thinking I had chosen channel 13) and suddenly I was able to pair all the devices that had been refusing to pair. Interestingly, before I had reset the Zigbee stick, I had tried pairing devices with the channel set to 20 with no success. So it seems that something had gone wrong with the configuration or data stored on the Zigbee stick that was only cleared out by resetting it. With channel 20 chosen, I then needed to change my 2.4Ghz WiFi channel again, so I've set it to Channel 1 for the least interference. -
Channel 20 - It's been about a week, and so far, so good. The Xiaomi buttons and the Peanut plug paired easily, as was re-joining all the other Xiaomi devices and my Sengled bulbs that were still on my Hubitat's device list. Since I now have an XBee that allows me to look at the map of my Zigbee mesh, I will be experimenting with Xiaomi devices connecting through the Peanut Plug (which works as a Zigbee repeater). I'm crossing my fingers that I don't run into the same troubles as mentioned above which required a Zigbee stick reset to get things working again.