If I'm not mistaken, Glenn Campbell used it on "By The Time I Get To Phoenix
and on "Witchta Lineman". He built a rep around using it. Also, I believe John Denver used it and Roger McGuinn revolutionized it with the Byrds. It adds a tone color that
the standard six doesn't have unless put through a Boss Chorus but then it sounds
electronic. Bob Gibson used it. I played Pete's 12 string for an afternoon and I think he may have picked up some ideas from me. Paul Simon used it on some of his recordings.

In my opinion, excluding some individual guitar makers, generally the best sound was the Guild. I loved the old Leadbelly Stella too but you'd have to have cast iron outsized hands to make it sound right.

The unique part of the 12 is the the thin third string is higher than the first which
feels like an overtone.

You can tell the difference between the acoustic 6 and 12 on recordings.

Try Thomastik 12 string sets on it.