Do you feel like that combination is enough to catch the points you want to catch? It appears to me that it catches the 8 points you have highlighted in yellow (maybe a little earlier or later than the yellow cell), but it also catches a lot of other highs and lows. I tried a 5 point window (=SLOPE(B2:B6, A2:A6)) and it caught fewer spurious peaks/troughs, but still caught the 8 highlighted. When I tried a 9 window slope (=SLOPE(B2:B10,A2:A10)) It still caught a lot of spurious points, but failed to catch a couple of the yellow points.

Anyway, if the 2 point window you tried is adequate, then good. You might try other windows and see if you like them any better. As I noted, there may also be other things that need to be looked at to get an algorithm that will catch fewer spurious points while still catching the points you want.