The banjo is inherently bright, brassy, cheeky, in-your-face and all of that; but it can also be dark and brooding, even menacing. Listen to some of Dock Boggs’ songs, such as “Oh Death” or “Pretty Polly.”
By and large, I am more likely to share pieces between harp and guitar than between harp and banjo. For example, it would not be odd to play the Bach Chaconne on harp and on guitar. The banjo is possessed of greater ‘tude (disrespectful). That’s one of the enjoyable things about playing three different instruments, all of them plucked strings but all different.