Punjabis were Muslim and Hindu before the Sikh religion was invented.
Ethnicity is defined by your mother-tongue/primary-language not by your geographic-location, caste/ancestory or religion.
Only the language you identify with defines your ethnicity, nothing else.
Punjabis of Pashtun descent are Punjabi because they speak Punjabi, they are not "Pathan", they are simply of "Pathan"/Pashtun descent.
Urdu speakers are Urdudan, Pashto speakers are Pashtun (even if they are partially of Arab descent e.g. the Mashwani tribe), Sindhi speakers are Sindhi...
Anyway these things don't matter, we're all born equal, nobody is better than anyone else, the only thing which can make us better is piety (taqwa) through Islam, and that is everyones own choice.
Islam's doors are open to you regardless of whether you're Punjabi, Kurd, Sindhi, Gujarati, Turk, Persian, Pashtun, Greek, Arab, Uyghur, Kyrgyz or Malayali.
Nobody is Neech-Zaat, nobody is born Ashudh or Apavitr in Islam.