Yeah the manga is still enjoyable even if rereading content you have already seen animated. There are plenty of chapters that were skipped during the first two seasons and that will no doubt continue with season 3 onwards.
List of adapted chapters for the first two seasons I stole from MAL.
Kaguya-sama S1:
Episode 1 > Chapters 1, 12, 5.
Episode 2 > Chapters 11, 7, 6.
Episode 3 > Chapters 14, 8, 9.
Episode 4 > Chapters 17, 18, 19, 20.
Episode 5 > Chapters 16, 23, 21.
Episode 6 > Chapters 24, 28, 25.
Episode 7 > Chapters 26, 29, 27.
Episode 8 > Chapters 39, 31, 55.
Episode 9 > Chapters 33, 34, 35.
Episode 10 > Chapters 37, 38, 40.
Episode 11 > Chapters 41, 42, 43, 44(first half).
Episode 12 > Chapters 44(second half), 45, 46.
Kaguya-sama S2:
Episode 1 > Chapters 30, 48, 57, 51.
Episode 2 > Chapters 52, 53, 54.
Episode 3 > Chapters 56, 59, 60.
Episode 4 > Chapters 58, 61, 65.
Episode 5 > Chapters 63, 64, 36 (not a typo), 66.
Episode 6 > Chapters 67, 68, 69.
Episode 7 > Chapters 70, 71, 73, 74.
Episode 8 > Chapters 72, 78, 79.
Episode 9 > Chapters 80, 81, 82.
Episode 10 > Chapters 83, 84, 85, 86. (also includes some panels from chapter 87)
Episode 11 > Chapters 88, 89, 90. (also includes some panels from chapter 87)
Episode 12 > Chapters 100, 101, 91.