Ahh - fires, flies, big apes, and beers aside (well maybe not the beer...), here's a great post from TK: https://budgetlightforum.com/t/-/34900/658, I'lll include verbatim here. This is what we are doing in Narsil:
Yeah, phase-correct mode on tiny25/45/85 is pretty awesome. It runs at precisely 15.6 kHz with nearly zero variation between units, it has none of the side effects of “fast” PWM, it’s fast enough to be invisible during use, and only a tiny slice of the population can hear it.
The main downsides are that it’s not quite beyond human hearing range, and it requires running the MCU at 8 MHz instead of under-clocking for lower power. I’d prefer 10 MHz / 19.5 kHz instead, but that’s not really an option with current hardware.
The common nanjg 4.5 kHz PWM is both audible and visible during normal use. 
Probably should mention the PWM rate in the OP - good info, and I'm sure people would ask.