Oh, i see that you mean central system: all lights, sockets… and also all switches go to a single main control unit. This system is a big “no-no” for me - although it’s nice since you only have one control system it’s PITA when this system dies. I’ve had a friend with such a system - when controller died during storm he ended up with totally dark house - he couldn’t turn on a single light or socket. Next day electrician came and wired so that some of light were on 24/7 until he managed to repair/replace controller.
I like separate controllers, which ARE connected to HA, but they can operate without being connected to it. That’s one of main conditions for me.
One other “down” side of central system is that you have to plan it before you do electrics, otherwise you must redraw all wires. Having controllers separate in each socket eliminates that, and you can add one at any time later.
A risk, yes… but way lower than power or internet outages and WiFi disturbance…
Nope, not according to my experiences. Whatever wifi problems i’ve had in the past it turned out they were all due to wrong settings on the router and they are pretty much gone now (and that’s with over 40 esp wifi devices running, plus phones, tablets, pc’s…). Of course, you need a decent router, not some 30-50€ model…
Otherwise thunderstorms in my region are by far more frequent than wifi problems. I have a few zigbee devices for a few months now also, and so far zero problems, even less than with wifi.