Help me with bishop pair stuff and this position please

I was white, and on move 17 my plan was to close off the bishop (kind of like in the Stafford Gambit) with the DSB. I couldn't play d4 yet or else Bxe4 would come. This explains the Re1 move I played in the game. I understand now that opens up the DSB to attack that rook. Going through Stockfish I threw out some what if scenarios and this like came up: 17. Nc4 Bc5+ 18. Kh1 b5 19. Nce5 Bb7 20. Qb3 Qe7

I did put in the b5 and Bb7 and I am wondering why this is so bad for black. I am seeing a 4+ advantage for white. And then the N sack with Ng5! Is that all this is? White has attacking advantage of 4+ or is there something else that gives white a 4+ advantage before Ng5?