How hard are pawnless endgames to win?

Playing against software, I can win with K+B+B vs. K and K+Q vs. K+N from the most unfavorable starting positions. However, with K + B + N vs. K, K+N +N vs. K  + P, and K +Q vs. K +R, I can win from positions fairly close to mate, but not from general positions. From what I can tell from the databases, most masters can win all of those I mentioned, but some master games result in draws. K+Q vs. K+R seems the most important, as it can often result from a rook pawn endgame.

I looked up how to win with a bishop and knight, but i dont know b+b tbh I think i just figured it out not too hard that one. k+k im sure is possible to figure out but between k+b vs k+k+k i wouldnt even know the knight and bishop video was fairly complex though. I think i heard gm hambleton from the chess brahs say he didnt learn k+b until master level

ohhhhhhh bishop and knight vs king+knight? Yeah impossible probably im a lowly 1270 though so perhaps it can be done still. Ive heard king and queen is very difficult vs king and rook too

K + 2B vs K is a theoretical endgame where the two Bishops checkmate, but I'd estimate about 1500 or 1600 level difficulty for learning that one. By all means, lesser rated players can learn this endgame, but just that by 1500 or 1600 level I'd more or less expect the player to know it by then. 

K + N + B vs K is even tougher. Master level seems a bit high, but it is certainly 1800+ to figure out and again it is a theoretical win by checkmate. 

K + N + N is NOT a theoretical endgame as this checkmate can't be forced. This is a draw. Mysteriously enough, K + N + N vs K + pawn might have a forced win! Yes, an opponent having an extra pawn might make the defending side lose to best play but without the pawn they can draw easily! That endgame IS probably titled player level and I myself never studied the intricacies in it (although I have glanced at it and it is very complex). 

The simple explanation there is that The two Knights and King corral the enemy King while one Knight also blockades the pawn. Then, at the right time, the Knight releases the blockade to give the opponent pawn moves and closes the mating net for a forced checkmate with King and two Knights before the unleashed pawn Queens and wins. With no opponent pawn present, the Knights can force a win due to stalemate. Even with the pawn, some positions are still drawn with best play, so even knowing what is "winnable" isn't easy to figure out!

Winning pawnless endgames can be incredibly hard as we found out with the help of computers in the past decades. Fortunately, by the rules of chess, the really hard piece endgames (like R+B+N vs R+B) do not occur a lot. To protect the kings from violent assaults in the opening both sides were given 8 pawns. Imagine playing a game without them! The pawns continue to play the protector role throughout the game until we reach the final phases (usually) when the much stronger pieces have often been exchanged. It is rare to have many pieces and just one or two pawns on the board - certainly on both sides. That's why most pawnless endgames feature just a few pieces. And because some of the pawns may promote the queen often reappears in that phase. So indeed, piece endgames like Q vs R, Q vs B, Q vs N are important. The last two are simple though. Less often the queen has to fight 2 other pieces because 2 pieces are more capable of stopping a pawn from promoting. The common pattern is that one side sacrifices a piece to promote a pawn. So I agree with post #1 that the Q vs R endgame is the most relevant one amongst the pawnless endgames. Learn it well, it is not that easy.