OEM Plugs are fine for most power situations. I would not stray from these unless you are tuning Well above what most tune for.
I had Brad, AJ Turbo, tune my 2015 SHO and he said just use the OEM heat range. I was tuned to a high 93 tune, E30, and FULL E85 tune. Brad said there was absolutely nothing to gain by going colder. Same with the Thermostat.
OEM plugs are inexpensive, easy to replace, and unless you are driving like a mad man. They will hold gap pretty well.
Iridium are not "Gap able ". Are these ? When tuning. You want to gap a lot smaller to avoid blowing out.
I am showing like $25 a plug. Yeah not worth it imho.