Hi what is the difference between a normal nord using the voice , a tuhum user and a dragonborn?

Do wild talents on the voice exhist and still not beeing dragonborns? So what is the jarl of Windhelm since he used the voice against the previous king?

A "normal Nord using the Voice" is the same as a Thu'um user, since the Thu'um is the Voice.

A Dragonborn benefits because they can directly comprehend a Word by absorbing the power and knowledge of slain dragons. They possess the innate ability to Shout as the Dov do, and are also able to learn Shouts quickly. That does not mean that a novice Dragonborn is stronger than a trained Thu'um user, just that they would learn faster. As the Greybeards show if you talk to any of them besides Arngeir, when they whisper your name, the entire mountain shakes.

Ulfric isn't a Dragonborn. He's simply a Nord who went and trained with the Greybeards for a couple of decades, and wound up learning two Shouts (FUS RO DAH and ZUN HAAL VIIK) before he left to fight in the Great War.