I don't think Tav/Durge really exists, how could they even be told canonically in further parts?
In DA there were always fixed heroes, the origins were also fixed, one gender, one race, class there are only 3, so it wasn't that difficult, in DAO we could choose from 2 genders and up to 2 races (mage origin), but BioWare clearly stated who was canonical. All DAO origins were canon, but only one managed to become a Warden, DAI was the same and DA2 only had one hero and both genders were canon according to BioWare.
I don't see that in BG3, except for the companions.