Not sure where you're coming from with this idea. The ignition system just makes a spark and this has nothing to do with the type of electrode. Electrode type influences longevity more than anything else. It's usually only the centre electrode that is made of exotic metal. Heat rating of the plug is determined by insulator length and design the of centre terminal. Correct installation is also important.Standard plugs unless you have upgraded you ignition, or grounding system, along with better wires. Our electrical systems are not meant for these Platinum 4's or what ever kick butt $6 - $8 plug they are selling right now.
We were talking about an LX Rio, I thought? No doubt high performance engines could do with a little ignition tweaking; no arguments there.Here are the brass tacks though. Do you have a high performance engine? High compression? Low compression with boost? Aftermarket ignition system? Do you have to run a different gap on your plugs? This is what you would need a smaller filament, or iridium for.
(PS they do have to put a resister in plat, gold and silver plugs because of the skinny filament)
You will also not notice a gain in HP or MPG unless your current plugs are just horrible. I would go with the NKG's so +1 for the 2382's.
Easiest way for quick and easy HP and MPG are Cold Air Intake, and Freer Exhaust.