#21
All endgames with 7 men or less are now technical endgames: these are known exactly.
Endgames with 8 men or more are practical endgames.
Champion w best Endgame technique?

#23
Use a data base and look for games with a high number of moves.
Aye , So 50+ moves decisive games ?

#23
Use a data base and look for games with a high number of moves.
Aye , So 50+ moves decisive games ?
That doesn't necessarily make it a decisive game, but a game that long likely has a lot of endgame to study.

Karpov, Carlsen, and Capablanca are the top candidates. All three have a very strong understanding of the endgame.
I would say Karpov and Carlsen are tied for first, though. Capablanca was incredible but he seeked to gain an advantage before the endgame. Karpov and Carlsen consistently squeezed water from stone with a few minor imbalances in technically drawn endgames.
Petrosian is an honorable mention. He didn't push in imbalanced endgames like the other three without an actual advantage, but he did often just wait it out until his opponent blew themselves up, which is kinda funny.
#23
Use a data base and look for games with a high number of moves.