You had the same experience that a lot of racers and hot rodders have, they don't hear it until the motor quits or starts smoking
I learned to look at the plugs frequently until I knew the tune up was safe
On my stock 415 HP M.W. on the old 100+ octane high lead pump fuel in 1971 to 1973, it liked the stock J11Y, not the J10y or the hotter J12Y spark plugs. I could hear the difference in idling right away, I could see the differences in on the plugs with one full WOT blast down the street
As far as heat on the plug tip the center porclyn determines what the tip temperature will be, retracted or projected
More porclyn around the center electrode less heat transfer