Looong and sweet! Probably the best study with this material. Also amazing with the black pawn on b7 instead of b6 where black wins.
White to move and draw

Looong and sweet! Probably the best study with this material. Also amazing with the black pawn on b7 instead of b6 where black wins.
My vote for the best study with this material goes to the 1915 H. Adamson study, which you agreed is also amazing. To me, the Gorgiev study is just the Adamson study turned into a draw because Black has lost the chance to play b6.
What I like about the diagram setting is the succession of dualfree moves right until the triangle landing with the king reaching c1. The lines in the other version are not as crisp once the move ... b6!! has been played. But it is clear that Adamson must already have known both settings in 1915 to find the 'b6--move' which virtually makes him the author of Gorgievs study as well!
Note: I do agree though that Adamsons study has all the content of the Gorgiev study plus some more, but one of the best parts is moved to a try-line - the one where black plays .. b5? instead of .. b6!!. It is a matter of taste on how to rate try content in relation to solution content. That's how problemists have different appreciations.

I find it somewhat surprising how few competitors the Adamson and Gorgiev studies have for best K+P vs. K+P study. Besides the Réti study, there are a couple of other possibilities below. Any others?
White to play and draw
White to play and draw
I have some more candidates in my Lommer books, for instance this one:
Less spectacular than Adamson when you look at the move b7-b6. There it wins the ending while here it is merely the most challenging drawing move. This to illustrate the significance of the context of 'spectacular' moves. But the terminating pawn moves in the main lines of Grigorievs study are beautiful as well!
Will continue this comment at some other time.
For interest I include the next ending of the K+P vs K+P type. It was mistreated by two grandmasters in the world class IBM tournament but in a cultural venue in Amsterdam, a leading jazz musician (98%, 1% chess player, 1% Go player) disclosed the winning move! By Solomon's rule he is therefore the one and only true author of this study.
How about bishop and 1 pawn vs bishop win
If you have interesting examples you may start your own thread for it. IMO, it is not appropriate here.

Something seemed familiar about that one (#10). Then I realized it's another setting for this study.
White to play and win
It is not the same. The critical move 1. .... Kd5!! is not there and cannot be there as the white king is too high up the board and the black king too low. The key move in Mengelbergs version is special in the sense that the king leaves a square in order to return there, a loss of two tempi where at most one tempo was to be expected (after check).
Of course the final pawn moves are identical but that is not the distinguishing part of Mengelbergs endgame. It is all about the one move at the start!
Note for instance that Mandlers 1. Kd6 is required to keep an eye on the double step of the black pawn which is not an issue in Mengelbergs version.
White to move and draw
Composed by Tigran Gorgiev (Russia)
Published in The Chess 1936