Looking at the info for those two sensors, it does appear that one of them is "normally closed" and the other is "normally open", but I'm not clear which is which, nor how to adapt one that's reversed. Also consider the electrical connector will have to be modified if it isn't the same. Is there a Miata forum with suggestions for optional sensors that can be used?
For the aftermarket ECU's (not your friends Miata), I believe most of them can be calibrated to use almost any temp sensor. But you'll need to know the values for that sensor to input into the ECU program. Over here where the MegaSquirt ECU is so popular they usually use a very common temp sensor from GM (American) cars. The values are well known and the sensors are easy to get anywhere for little money.