Won’t work sadly, the “counter sound” can’t be in phase in multiple locations because of delay and reflections. Headphones can do ANC because the ear is basically a single point so the mic can pick up exactly what you’re about to hear and then compensate.

Using a speaker like that would just create double the leafblower noise.

Do you live in a warm country?

I think for straight 4/4 (so not felt in half time) 140 and above is definitely fast, considering the vast majority of music falls in the 110-130BPM range.