Unless the engine is requesting the higher spark energy or something exceeding the original design spec due to modifications, etc, you will gain almost nothing by using the iridium over double platinum spark plug on the NSX engine with the standard INJ spec, OEM IG coil/dowel time, fuel pressure, etc.
For the clarification, iridium plug will very likely to have some benefits over the classic standard one.
With our NSX engine, most likely, you will be replacing the plug before the recommended maintenance interval not because of the plug itself but due to moisture getting inside the plug hole especially at the rear bank.
In Japan, NGK doesn't even list the iridium, the latest ruthenium or even the classic standard spark plugs when specifically searching for the plug for Honda NSX and only lists the PFR*G-11.
This is because they always recommend using the specified OEM plug by the car manufacture or the one recommended by NGK for the specific make/model.
You will only see the alternative options such as the iridium, ruthenium ones when searched for the compatible models for the PFR*G-11.
They need to protect themselves from the unknown factors when recommending the alternative ones so always check the small prints.
Please note that with JDM NSX, it never received the 3pin IG coil and stayed with the 2pin style and thus, no changes in spark plug spec (PFR*G-11).
Outside of Japan, depending on the country spec and the year model, you may have PFR*G-11, PFR*N-11 or PFR*L-11 from the factory.
Years ago, I contacted NGK Japan asking about the spec difference between these 3 but due to IP reason, they were only allowed to say that they were based on the design requirements provided by Honda so must be something to do with the changes in misfire detection or something.
On NGK website outside of Japan, when you search the plug for Honda/Acura NSX, it will include the compatible alternative option addition to the OE spec PFR*G/N/L-11 and you'll even see the ancient ordinary standard plug included.
Again, you'll always see the small prints if using these alternative ones.
So, you can use these alternative options over the OE spec but doesn't have to.
Just be careful with the recommended service interval when using non-double platinum one.
Some, including the specific iridium one has much shorter life cycle.
Also, with 2pin style IG coil, make sure to check the shape of the top terminal of the non-OEM plug.
Never use the one with a hole (popular with removal/screw type top terminal) or deep dimple.
It can chew into the spring loaded 2pin IG coil internal terminal and eventually cause failure.
There are many fake NGK plugs on the market.
NGK has many factories around the world and using different packaging so it doesn't help….
Kaz