If I recall, it has to do with humanity’s DNA. The double helix spiral somehow grants us boundless potential and makes it so we grow quickly. Simon’s drill harnesses the potential of spiral energy, which in itself can be described mostly as potential energy.

You can completely ignore it. As far as a power system goes, it’s about as nonsensical as Haki, and using spiral energy is mostly just about wanting to win more then your opponent. It’s just a convenient way to make the final conflict be a clash of change vs stagnation.