Will i feel fatigued in my workouts if i eat 100g of carbs per day? i am a boxer & workout very intense every day.

No one knows: Can anyone else know how you will feel? No way, vastly too many variables. Docs have no such god-like sophistication, despite any claims otherwise; the whole reason for clinical trials. Plan out, track & do your own personal trial. For whatever results you observe, does this mean someone else nominally similar will react and perceive the same? Absolutely not, far too many individual variables.