We could add some of that to the documentation.

In terms of voice codecs, we use G711 exclusively at this point. Later we may add some others, but for now we want to focus on that since it's the highest quality and we have plenty of BW.

Three way calling does double the BW usage.

For faxing with a fax machine connected to ATA, we've had a lot of people having luck with it, but it's always going to be hit/miss. The best bet is to set the send speed to the lowest possible speed on the machine.