Three years ago I tried an expensive Linksys Triband Mesh System that was well reviewed to replace my aging 6th gen AirPort Extreme that would have drop outs and poor performance, but only sometimes.
Normally I would troubleshoot, but since my 6th gen AirPort Extreme was pretty old at that point, I figured that I would replace it with something modern.
Basically, the Mesh System actually performed worse than the AirPort. The issue had to do with congestion with the 2.4Ghz band in my area rather than a HW issue with my AirPort Extreme, after splitting the 2,4Ghz and 5Ghz band, and moving all my devices (that was compatible) over to the 5Ghz band, my performance was amazing. No drop outs, and really fast speeds to even an ATV that was two floors away from the router maxing out the ISPs 300Mbps speeds.
I also had roaming issues, which was one of the main reasons for getting a Mesh System. I wanted to have Wifi close to where I parked my car in my old house, so had a node as close as I could get to it. Issue was that my iPhone would stay linked with a different node and not automatically switch to the closest node. The signal sucked, worse than my old AirPort which would sometimes work at my car.
For the Linksys Mesh System, I talked to customer service for hours trying to make the performance better, making sure I didn't have a defective node, and their solution was to do what I did with the AirPort, split the bands. Their solution for wifi at my car was to turn off the wifi on my phone and turn it back on.
Yes, their solutions worked, but not as convenient as I would like nor what I paid for. This was especially true because the AirPort actually out performed the Mesh System even with the bands split on the new mesh system. I was paying for
I ended up returning their crazy expensive mesh system, and bought another AirPort Extreme on eBay for really cheap and moved it close to where I parked my car, solving that issue.
I have since bought a different home, this time a single family home, and have expanded my AirPort Extreme pseudo-mesh system to FIVE 6th gen AirPort Extreme units and one AirPort Express.
I replaced my 2012 Airport Extreme
the 2012 Airport Extreme is still a great router sending a strong wifi signal.
Pretty sure you have the 2013 AirPort Extreme.
I have a AirPort Extreme and airport express?
I have my AirPort Express on the same network as my AirPort Extremes, and they work fine together. I had issues in the past which I thought was related to my AirPort Express being only the older "n" wireless, but I am pretty sure all those issues had to do with my story above, the 2.4Ghz band.
I mainly use my AirPort Express as an AirPlay 2 device for a sound system, but no issues with it at all since splitting the band.