Interesting comments like you can change any thing, Once again costing into view here as in why did you change that plug for its got plenty of meat on it left. Champion state that when the plug is half worn its U/S. Generally before this you don't have any problems with plugs. Now one thing you half all missed that when a mag fires it has multiple discharge, It is not one spark but several. Also you have positive spark and negative sparks, this means that it fires from and to the centre electrode and this gives different wear patens. 4 cly engines a plug will not change per cylinder. Meaning that #1 cly will be a positive spark and #2 will be a negative. Now a 6Cly each time the plug fires it will be different one fire pos and the next will be neg and this gives a more even wear on the plug.
Next thing is if you follow the manufacture advice and have you mags and plugs change and serviced you really don't have a problem.
As for gapping you can gap both types of plugs period.
Now depending on the operation of the aircraft what engine it is there are variables to everything . The worse plugs for fouling I've found is training aircraft.
As for anyone being able to say that they can feel an engine with high gaps I truly find this hard to believe what was the engine ? The only way I know anyone can do that was on the large radial engine s that had oscilloscopes and the really good flight engines could pick which plug it was on a 28 cly, before my time but can remember story's and reading about it as a an apprentice