I don’t know about the serial versions, but there already exists a thread: High power LoRa modules
As for HAM license and transmit power: It’s the same in germany. You are only allowed to transmit with higher power if you communicate unencrypted. Encoding is a different thing, but the encoding/modulation/whatever method must be “well known” to be used in this frequency range and context. So you can’t just invent your own encoding only you know. That gave me the idea that if we’d make it public and a “thing” that meshtastic is used on HAM frequencies (in germany the 433MhZ LoRa freqs and HAM freqs conveniently overlap) this would be legal and people with a license could transmit with up to 750W (lol) here. From my understanding deleting the psk would be enough to strip the encryption?
BUT: Transmit power is not even that important. I tested it with around 100mw and 6-7W and the difference was not as big as I had expected. A good antenna and antenna placement is much more important.