The wiring document will be your new best friend.
https://s3.amazonaws.com/miata/miata/1990+Wiring+Diagrams.pdfLearn how to read it and make sure you mark up any changes (radio, air bag, HVAC delete) you make. I have pictures of my marked up copies in case I loose the originals.....yes they are that important.
I used the left hand stalk and it keeps all of the stock Miata functionality (headlights, turn signals). I removed the right hand windshield wiper stalk. I actually kept the hazard/headlight-pop up switch. The hazards switch I left unchanged, but the headlight pop-up switch now runs my windshield wiper motor. Since I used LED taillights are had to do a mod to the blinker switch. Link here:
https://forum.miata.net/vb/showthread.php?t=335534