We're big fans of LED lighting. It responds quickly, it generates almost no heat, it lasts for a long time and it uses minimal power. What's not to love?
We use LEDs from Diode Dynamics because they're the best ones we've found. They're made in the US to high standards, not just the minimum price. They've got constant-current circuitry to protect the bulbs from transients and offer a three year warranty. Even their lumen ratings are based on actual measurements instead of advertising promises. You can buy cheaper LEDs, but you can't buy better ones.
Please note that the 310 lumen turn indicator bulbs are physically larger than the 280 lumen ones, and will not fit in the rear housing of an NC.
About hyperflash: the flasher in your Miata expects some resistance from the light bulbs. If that resistance isn't there, it will flash faster, like you have a blown bulb. That's a clear sign of someone who has replaced their LEDs but hasn't paid any attention to actual function. It's a little embarassing to see. The solution is to add inline resistors - you'll need one pair of resistors for each pair of flasher bulbs, or two pair for the whole car.