I recall hearing that there are differences between a neshama or nefesh yisraelit and a neshama or nefesh yehudit in a metaphysical, kabbalistic, drush or sod sense and I would like to know what those differences are? and also more about this topic in general and what the sources are. I may not be using the precisely correct terminology and I also searched through previous questions and could not find a similar question.
There's no difference. The term “Jew” or "Yehudi" stems from the tribe of Judah (Yehuda), for most of the 12 tribes of Israel were lost in the Assyrian exile, and therefore, most of the People of Israel today are from Judah, hence, we’re called generally: Jews, but it's really more accurate to say: Israel (which also includes Kohanim, Levi’im, and Etheopian Jews who are all not from Judah, but are as "Jewish" as every one else). The two have been used interchangeably throughout the sources for the past 2,500 years. Only recently, some anti-Zionist or anti-religious have begun to differentiate between the two, in order to degrade those whom he doesn't like, but this strange coalition is not historically based, and contradicts all of the sources.