Redundancy. Make sure two or more sensors agree, else you have a fault.
It is. I started my home automation using MQTT and Tasmota firmware on the devices, but ESPHome is so much easier to set up on a device and integrates very well into Home Assistant. If you are going to have a number of devices identical except for the device name, this line: name_add_mac_suffix: true in your devices’ YAML code adds the MAC address as a suffix to the device name, so you can install identical code to all of the devices.
I bought a wt32-eth01 and flashed ESPHome to it. Easily done, but it’s still in my drawer as I don’t have an application that needs the reliability of Ethernet. In your case it may be worth investigating further.