If I understand the history correctly, Nordic poles are just poles. Different grips (cork, or the fun paddle shapes as with the Pacer brand). Nordic refers to the style of motion -- like Nordic skiing (which combines cross country and a telemark version of downhill) -- and the nordic poles seem to have developed initially so that competitive skiers could maintain conditioning during warmer months.
I am mixed on the "anyone can use the poles any way they see fit" -- for while I don't care one way or another in some respects, in others I am always concerned for anyone's well-being and the poor technical use of equipment that can lead to injury.
I see many people using their poles as though they are trying to climb an icy rock face, hauling themselves forward, and I see rotator-cuff injuries just waiting to happen. And then I see people who seem to plant the pole at about the mid-arch as they move the foreleg ahead, and that seems to be a nasty trip hazard....
I did take a few days to learn the Nordic technical use and I'm not as fast with them as without, but with proper technique I keep my gait straighter, and remove pressure from the lumbar spine and the knees.
In the end, get what suits you, what is most comfortable, easiest to transport etc etc. I have the carbon-flik-Z from Black Diamond with the vented double grip... but that's me. I use them almost every single day and they are 4 years old now.
As to the "click click".... I love that sound. I have rubber tips on my poles and don't generally click, but the click click means to me that other people are finding their freedom, walking into their own futures... and so I have actually come to enjoy it.
People chewing with their mouths open, talking with food in their mouths, or snapping gum, however; that makes me berserk.