I generally use what the OEM recommends. The OEM I worked for actually did testing with different plugs and brands to see which the engine ran best on, if any. Perhaps they don't all do this, or do this anymore, I don't know.
The only exception is flat head engines. The small Briggs I have I use narrow electrode plugs. We tested them at work and eventually recommended narrow electrode plugs for flat heads. They concentrate the spark, which helps low compression, volumetrically-inefficient engines combust. They start easier & faster, and run smoother.
I wouldn't use coated electrodes - the purpose of coating is to make them last longer (less metal transfer across electrodes). The coating isn't as electrically-conductive as the base metal of the electrode, usually a copper alloy. Coated electrodes are targeted at high hour use engines such as automotive engines that have high voltage ignition systems that can power through the coatings. A small engine may not run as well on them, plus you don't put the hours on them like you do with a car, so you spend more money to make your little engine run worse, and it's only one or two spark plugs anyway.
In fact, the Gen III Ram HEMI engine originally had to use uncoated spark plugs that had to be changed every 30,000 miles because Chrysler didn't put on a big enough coil pack to fire the 2 plugs per cylinder needed to meet EPA exhaust emissions! They since put in bigger coils and now use coated plugs for 100,000 intervals. I change at 50,000 miles - they get fairly pitted by 100,000. I ran both engines. It cost $300 to change plugs!!!