Anyone want to share their experience with the Mini 3 and Nano 3S?

I'm considering buying a few of these to replace heaters in rental houses, but I'm a bit concerned about stability.
I've seen several people posting about different issues, but I'm not sure if those are serious issues or not.

The houses in which they will be placed is far away from where I live (7 hour drive), so I can't be driving back and forth to fix minor issues, they need to be stable.
I saw that the app only works if you are on the local wifi (which is a shame and missed opportunity for customers like me), but I guess I can manage them through a VPN.
I assume they can be managed through browser on IP, in addition to through the app?

Any feedback is welcome, thanks!

PS: I've been locked out of my Bitcointalk account for years, finally got it back today!