charlie
I dont think they will support WPA3, They use an older ESP chip and I dont think its wifi stack supports it.
In the wifi Component documentation for ESPHome it also notes that WPA3 settinga are for “ESP32 Only” which would back up this thought.
I am pretty sure you can switch back and forth between firmwares with OTA flashing without issue. there is some notes on this in the knowledge base somewhere.
The link you sent is specific to you and long dead.