There are several required modifications you must do when converting a Miata to a racecar. A big radiator is one. Racing brake pads is another. Another must-do item is removing the parking brake mechanism to reduce drag on rear pads.
Yes, you can pull the E-brake adjuster screws on the caliper all the way in, but then your E-brake doesn’t work anyway, so you might as well remove it. When you do, it also removes about 5 pounds of weight, always a good thing.
Truth be told, the job itself isn’t much fun. You’re on your back under the car for a lot of the job, and once you start in on the rear brake calipers, it’s messy. Because of the dribbling nature of brake fluid, it’s not really possible to keep things clean and tidy for this job. Have lots of brake cleaner and paper towels on hand.
To give it an overarching trajectory for the job, you essentially remove the hand-brake lever inside the car, remove a heat shield under the floor, the cables and the brackets that retain them. Then you move to the rear axle where you remove the cables from the E-brake levers on the back of the calipers. At that point, you remove all the cables, then pull the rear calipers off, disassemble them and remove the parking brake mechanicals from inside the rear caliper pistons and then reassemble the calipers with new seals. It’s a fair amount of work.
One piece of advice is to buy the caliper rebuild kits from Mazda. They cost more, but they have all the pieces you may or may not need. It’s also important to point out that the Mazda kit services both rear calipers, not just one, which helps explain the difference in price.