They seem to have a good grasp on one of my pet topics in modern American popular music: melody. Their melodies have a good balance of continuation, repose and finality, which has basically been abandoned in most R&B since the late 90s.

The trap they've fallen into is an over-reliance on earth tone vibe and that top-of-the-throat breathy lullaby thing you mentioned. If they could bring the melodies down to where they're singing from their diaphragms, that would be a great start.

I really like their chordal movement, too. I haven't read up on them yet but I'm guessing at least the pianist has studied music. Nowadays, studying theory and composition is one of the only ways to learn about how to do any of this, because it's largely vanished from anything that's a new release on the radio. Well, you could also have super high innate talent too, but that's not even really that necessary to create good music if you've been taught the right things.