It's not like a 1600 will have much worse endgame skills compare to an 1800, they will be worse, but not by much. An 1800 will have slightly better theory knowledge, endgame skills, tactical vision, etc. They will likely just be slightly better in everything.
Although there is one key difference that I have noticed. The lower elo's always will always play the more "obvious" move. Let's say their opponent just took their pawn. The 1600 will immediately take back without hesitation. An 1800 or a 2000 will look a bit deeper. Perhaps look for a zwischenzug, or maybe even to gambit the pawn.
Let's say you're considering sacrificing a piece for an attack on the king. The 1600 will calculate, but they will get scared if they run out of checks for a move or two, and will likely dismiss the idea. The 1800/2000 will actually look deeper and see if it's actually an issue. The 1800/2000 will see that the king is incredibly weak, and there isn't really a way for it to escape the attack. They're also much more intuitional.
A 2000 player could beat a 1600 with minor piece odds consistently and a 2000 player could beat an 1800 player with 2 pawn odds consistently. an 1800 player could beat a 1600 player with 2 pawn odds consistently.
How do you know these things? I would not feel comfortable being two pawns down against players two hundred points beneath me...the reason I beat them is that that doesn't happen very often to me