Sorry we skimmed over your already-bolded question! I think I remember spending a while recalling a C++ maths library one of my maths lecturers mentioned, never got to it 
Since you’re writing it in C++ on a fast Arduino, you’re already going to be quite fast, the only thing I’d recommend giving a look is the ARM CMSIS libraries, they are optimised for the Cortex chip in your Due, and have quite a few signal processing functions available:
https://arm-software.github.io/CMSIS_5/DSP/html/index.html#intro
Since Glowbits are based on the common WS2812Bv5 LEDs, most of the regular suspects for the Arduino (FastLED etc), work just fine, and we mainly wanted to support the beginner-friendly nature of microPython. For an interesting dive, we’ve published videos on the challenges of getting speed out of microPython: https://youtu.be/zC-vDwFpGXU
