As a harmony singer and composer I think he held his own with his bandmates, and IICORMN has remained one of my favorite albums since its release (and it has long been included in TAS's recommended LPs, for good reason--Croz noted that the engineer Stephen Barncard was the best at recording acoustic guitars). Qobuz's HR version of the album is indistinguishable from my original vinyl on my system, which has an excellent turntable/tonearm and preamp. The 50th anniversary version has some interesting alternate takes, outtakes and demos.
Croz showed his jazz influences more than Stills, Nash or Young, and the unusual chords he used in some of his songs reflect that. Like Joni Mitchell (and probably due to her influence) he often used alternative guitar tunings as the basis for his own songs, and those tunings facilitated unusual chord choices. He sparingly produced one or two of her earliest albums.
I saw him live several times with CSN, CPR and Nash, and he was entertaining, although he seemed more introverted/low-key after he cleaned up. CPR and the band with Nash were great bands--he knew good musicians when he heard them. Some of the bands and performances during the freebasing stage of his solo career were less appealing to me.
I recommend Croz's autobiography Long Time Gone for an intimate glimpse into his life and the colorful times in which he lived. He even includes a psychiatric evaluation of himself from around the time he was ending his addictive lifestyle. Now that's being open!
His Voyage anthology is excellent and in HDCD format, for those of you who have players which support that format. I think it does sound a bit better than Redbook, having compared the two on the same tracks, but not as good as higher-res formats.