They don't perform better. They only allow leaner mixtures because they don't foul as easy nor wear as fast. So yes, you can gap them diffeferently then re-jet your carby to run slightly leaner. If you keep your A12 tuned well, and re-gap the plugs every 12 mos, I see no need for platinum. If you want to gap them once every five years, then get double-platinum (or iridium).

Regular platinum only last about 35,000 miles, Double-platinum plugs last 100,000 miles.

Best plug is a 0.13 mm gap plug which can only be used with a high-energy ignition (like the stock B310 dizzy upgrade). Large gap will allow a lean mixture to more reliably burn. Note that Nissan used 0.11 gap but the matchbox is good for 0.13 gaps. Maybe the E15 dizzy is good for same. You can use this with regular plugs or with platinum, the regular will need more frequent re-gapping.