The point of Bard is that he isn't understandable in terms of how he thinks or goes about things; he works with intent and purpose, but it's not something you can easily glean just by seeing him. I feel like that's the appeal of Bard.
Even then though you can see there's character to him in the way he behaves, be it in the game or in his main lore appearance, Bard: Mountain. Big things like the way he moves, how he physically reacts when laughing, even the tiny things like him spinning his horn when he went to port the shrines on the mountains away, shows there's more to him than you can really see. There are things to Bard we can gravitate towards and say "yeah he's like this", but at the same time those things are just our interpretation of how he operates.
Bard's strength of character comes from him being wholly inhuman and incomprehensible. I mean to many people Bard seemed like an arse for ignoring the Bards on the mountain in his cinematic, but Bard works with purpose, and our human interpretations are just that, interpretations.
For that reason I feel like we already know what Bard's colour text and full bio will be like; references to times he's appeared in history and cultural interpretations of him, but not a true origin. Like Kindred's bio, essentially. Bard's a character who's cool not because of where he came from and what his personality is like, but because of what he is, the concepts he represents, and where he's going.
Really that's a long winded way of me saying is that your desire to have Bard be "understandable" is kinda missing the point of Bard. Understanding Bard isn't the main focus, it's what he does and where he's going. The mystery behind how he thinks, acts and behaves is part of his charm and a core part of his character.
