My understanding is that a radon reading of 2 is the upper bound for reasonable regular exposure. If you're seeing above that, I'd be inclined to look into mitigation.
There's an esphome config for them and esphome let's you set a password. I believe it supports encryption but I can't remember.
The faikins are really awesome. I have mine set up in Home Assistant and I have automations for them to do stuff to turn off if the outdoor and indoor temps are both pleasant. I also have it set up to turn off if any of my windows or exterior doors are left open for more than five minutes. But you can program them to do so much. The stock firmware does mqtt so it's quite versatile.