Well that's reassuring lol, thanks. So its just a matter of figuring out how to command the neopixels correctly, then.
Frankly I'm not sure precisely, but in theory the leds would update the fastest when in 1st gear, full throttle, as rpm will then increase the fastest. This isn't to say that in testing in neutral sometimes the revs will increase quicker (i set the base activation to 3000rpm for testing), but ideally neither scenarios should freeze up the system. Perhaps ill try and record some video of the tachometer to try and get an idea.
That's a good idea about the dimmer delay, im not exactly turning the headlights on and off all the time so there's no need to check for it constantly is there.
When I first created the sketch, a couple years ago, I attempted using 'else' if' statements and I distinctly remember them not working. That said, I am more knowledgable now so I'll give it a go. I understand what you're saying about minimizing calculations, I agree this could be improved.