Both homes had 2 furnaces. I can control both thermostats from my phone.

One of the ecobees in the old home had an Alexa built in. We never used it. I’d recommend saving the money and not buying that version unless you want to use the voice control to adjust the temp. We just used our phones.

I can’t compare them to the nest because I’ve only owned the ecobees, but I’ve not had a bad experience with them yet.