Carey is written for James Taylor...I think they had a vacation together in some exotic place that was the topic of that song

"Carey" is set on the Greek Island of Crete: "...and they're playing that scratchy rock'n'roll beneath the Matalla moon." Matalla is a place with ancient cave dwellings which were a favorite hippie hangout in the 60s and 70s.

The song Triad by David Crosby was supposedly about David's love for Joni while she was with Graham Nash. David Crosby produced Joni's first album...

If you listen to "Triad" it's obviously about David and two women.

Cheers,
Michael