Thread mics are good, but like all measuring tools, only as good as the hands and mind operating them. That said, there are a couple of things that come to mind that are advantageaous about thread mics over say, a set of thread wires.
First, you eliminate the wires, which can be clumsy to use. I typically use grease to hold the top wires in place , then hold the bottom wire with one hand while using the other to adjust the mic. A bit more juggling than a novice would be comfortable with. In the hands of someone used to it, the wires can be very accurate. But trying to get astraddle of all three wires evenly, plus find the max diameter, and keep the mic pressure just right, then do the math. As I said, for the experienced hand at it, the wires work great. But for the novice, it's a learning experience.
Second thing I dislike about the wires is that they add one more interface for the introduction of a foreign particle. Not a likely scenario, but still possible. The tolerances that your shooting for preclude any grit or the tiniest chip, which could still get between the thread mic anvil and the part, but add the wires in there, and that foreign object has one more place to hide.
You still have to be sure you have the proper anvil if your using thread mics, or the correct wires if you using those. So that's a wash. Your thread mic should read direct in Pitch Diameter, while wires have to be run through a little math. Slight edge for the mic. Thread wire sets are vastly less expensive and more adaptive than thread mics. You can get a set of wires to measure nearly any thread you can come up with for less than a set on anvils for a thread mic, plus the wires don't require a special standard, so economy is on the wires side. The Machinist Handbook will be applicable to either method, so it's a wash. You need one anyway, trust me. Boring as watching paint dry as far as reading goes, but a treasure trove of information. Get one. The info you seek is under thread pitch diameters, and not only will the book have the PD that you need, most likely, including tolerances, it will have the formula for figuring out the pitch diameter for anything it doesn't list. Get you calculator out and have fun.