NOx and CO2 are both odorless colorless gasses. Any "stink" is strictly HC.
The E3 plugs seem like a good idea at first glance, but some of their claims fly in the face of physics:
Reduced time delay in flame growth - shorter path to piston head
The flame front advances at a more or less fixed rate regardless of the nature of the ignition source. Once the fuel directly in contact with the spark starts to burn it excludes all oxygen in the vicinity, making whatever the spark does after that moot.
While they claim all sorts of advantages from their plugs they primarily focus on small engines such as leaf blowers and lawnmowers which are obviously not emission controlled and therefore pollute like crazy (The average leaf blower pumps out as much as 500 times as much pollution as a modern car. That's not in PPM of exhaust, that's total
amounts!) A 10% reduction translates to 450% more pollution. Whoopee. A rake only makes the user emit a little more CO2 than when at rest and drinking a well deserved beer, which BTW also emits CO2.
Note that none of the links they provide take you to any information from the EPA. Interesting.
There is no way to substantially reduce any emissions or make more power with different spark plugs unless the plugs that are in it are very worn.