"Gameplay wise, the start of the level is set to 100BPM; which is most likely why it feels very sluggish, and there being a delay between button press and an action occurring - since everything is on beat. Perhaps I should have increased the BPM after the first encounter, so that it's not 100BPM until the boss fight."
I'm actually referring to when trying to press them on beat. I would press in what felt like in time but was always slightly off.