[Walt Fricke]

You are overthinking this. Leave those round "nut" like pieces on the ends of the plugs. They are there to let the plug connectors grip. Your spark plug wrench will fit over these just fine.

You are looking at the hole which is machined through the cooling fins of the cylinder head. Your wrench fits over the hexagon, which is the spark plug itself.

Some spark plug sockets have a circular magnet to grip the plug's metal hex once it is threaded all the way out. Others have a rubber ring which grips the white ceramic part to do the same thing. But if a plug is unscrewed and gets loose down in that hole, you can fish it out with a magnet or some other simple tool.