I think this is a big thing I was missing. I know the HE can do up to 32 devices and I knew you had to add routers, but I thought each router could also do 32 so I figured I was fine. From what I'm hearing, routing devices can really only handle 10-20 which makes more sense why certain devices are failing randomly for me!
I usually limit each router to 6 devices. Gives them a little headroom if things ping pong around.
That's for a different model, which is why it says "view newer model". It's only showing the bottom of the page from my screenshot since that is all that would fit.
I have one of these Centralite plugs which seems to work quite well in my garage, repeating sleepy devices.
innr are zigbee 3.0 so in theory they should be some of the better ones you can get.
i certainly wouldn't buy anything that isn't 3.0 anymore.