I haven't heard anything on the subject of applicable races either, which is a good thing as hearing nothing implies that any race can have "hearers". The only ingame ones we see are I think hyur and elezen, but that's probably just because Gridania is the nation that primarily teaches/cares about conjury and its almost entirely made up of elezen and hyur (with a few keeper miqo'te)
as for if everyone born with the talent ends up becoming conjurers? I think they have to be somewhat in tune with conjury in order for their 'hearing' skill to reveal itself, even if it is an innate talent. This is drawn from Sylphie in the Conjurer plot line, she only starts hearing spirits after she finally starts to work with and actively listen to nature. That being said, I don't think a hearer has to be a well trained conjurer, and they certainly don't have to be an official healer. I mean, no one has to be an official anything if they don't want to. They do probably need to be capable of the very basics of conjury though, if they are actually going to be hearing anything. At the same time, that would mean someone could potentially go through their whole life having the hearing gift and never know about it if they never trained in conjury.
as for if everyone born with the talent ends up becoming conjurers? I think they have to be somewhat in tune with conjury in order for their 'hearing' skill to reveal itself, even if it is an innate talent. This is drawn from Sylphie in the Conjurer plot line, she only starts hearing spirits after she finally starts to work with and actively listen to nature. That being said, I don't think a hearer has to be a well trained conjurer, and they certainly don't have to be an official healer. I mean, no one has to be an official anything if they don't want to. They do probably need to be capable of the very basics of conjury though, if they are actually going to be hearing anything. At the same time, that would mean someone could potentially go through their whole life having the hearing gift and never know about it if they never trained in conjury.
RP scrub incoming 