I saw this question in its first iteration, and the answer is that the Treaty of Westphalia did not really concern itself much with Jews and the Treaty had very little impact upon Central Europe's Jewish population. The idea of cuius regio, eius religio (whose realm, whose religion), which the Treaty enshrined, was largely about the Christian faith; much of the ink spilled in treatises on religion focused on Christian believers. Judaism was not just a religious practice in early modern Europe, but a social and legal category that was largely immutable. Jews in the seventeenth and eighteenth centuries might convert to Christianity, but it was unthinkable that a gentile could legally convert to being a Jew. If anything, the Westphalia settlement entrenched the idea that individual sovereigns, whether family heads or corporate bodies, had the right to govern their Jewish population as they saw fit.

What this meant for Jewish society in Central Europe was their status typically remained that of tolerated aliens whose residency always could be revoked. On the more extreme end, some sovereign states did expel their Jewish population, such as Vienna in 1669/70. On the other end of the scale, the Margrave of Brandenburg-Ansbach and the Duchy of Pfalz-Sulzbach encouraged a degree of toleration and welcomed some Jewish refugees in the eighteenth century. But most elite opinion on the Jewish minority favored a rigid caste system of circumscribed professions, ghettos, and strict social segregation. In many parts of the HRE, Jews were a population apart from their gentile neighbors , both physically and culturally. For example, when the Hamburg council decreed in 1689 that the city's Jewish merchants were to keep business records in German instead of Hebrew, the Jewish city elders responded that very few Jews in the city could read German let alone write it.

This was not to say that Jewish life in central Europe was static in this period. Despite the presence of restrictive laws and the ever-present sword of Damocles of expulsion, Jewish and gentile life became more intertwined in the post-Westphalian period. At the apex of Jewish society were the so-called Hofjuden (court Jews) who provided funding for various princes and sovereigns. The strictures of the Baroque period demanded a prince spend a prodigious amount on cultural production and various state outlays, and some Jews like the Rothschild family were able to help these monarchs out. But these successful Jews were a distinct minority of a minority, Hofjuden and their dependents were at best 2% of the HRE's Jewish population. Moreover, their success helped add to new Jewish stereotypes of controlling European finance and other unsavory connections of Jews with money that already existed. The middle strata of Jewish economic life was divided between older professions of licensed hawkers of finished merchandise, merchants with connections to other Jewish enclaves, money-changers, pawn shop owners, and newer professions like tobacco and silk concerns. The growth of this middle strata was of course highly mediated by various antisemitic restrictions and periodic extortion by sovereign entities in need of quick cash. These various restrictions helped contribute to the problem of Betteljuden (begging Jews), itinerant Jews who operated without a license and made their way to various principalities. There was often little place for the younger sons of Jews under the restrictive antisemitic regimes that mediated Jewish economic success, which helped contribute to vagrancy. Moreover, the success of some of this middle strata often taxed the restrictive residency laws that characterized many central European cities. Census data from Frankfurt am Main's ghetto at the end of the seventeenth century indicated some 3000 Jews lived in approximately 200 houses. Even though Frankfurt was at the extreme end of ghettoization, it does demonstrate the problem of urban crowding for Jews that contributed to the expansion of Jewish vagrancy.

But even mediated economic success brought Jews and gentiles together in an unprecedented manner. There was certainly greater intellectual contact between Jews and and their Christian neighbors. The maturation of Protestant theology renewed an interest in the Old Testament and Hebrew as theologians sought to recover Christianity's roots. The rise of interest in both the occult and esoteric knowledge in the eighteenth century stoked investigations into Kabbalah and other forms of Jewish mysticism. Young Jewish men also became more tapped into the intellectual life of Central Europe. The rise of Hofjuden and other isolated instances of Jewish success provided an alternative model for Jewish identity away from Rabbinic or religious education. The Haskalah (Jewish Enlightenment) had its roots in the 1700s in part as a reaction against the control of traditional Judaism on Jewish intellectual life.

But these intellectual connections did not erase the massive restrictions and antisemitic prejudices. Theological interest in Judaica did not translate into Judeophillia, and various religious tracts and publications made frequent use of antisemitic language and stereotypes. Moreover, Jews were seldom allowed into central European higher education and had to go abroad if they wished to participate in the growth in European higher education. Kant in Königsberg was atypical in his acceptance of Jews in his lectures, but even then there were limits for this Enlightment philosophe. Jews in his lectures had to attend as nonmatriculated students and could only graduate if they converted. On a more quotidian level, the growing commercial interests of Jews also brought them into greater contact with the gentile world. Knowledge of written German soon became a prerequisite for Jews and a number of successful Jews chafed under control by traditional Jewish councils who ran the internal running of Jewish society on behalf of gentile sovereigns. Yet, despite the visibly increased wealth of some Jews, they were always in danger of having such riches and power taken away. The fate of the Hofjuden Joseph Süss Oppenheimer, immortalized in the infamous Nazi propaganda film Jud Süss exemplified the dangers Jews operated from in this period. Süss was the chief banker of the very profligate Duke Karl Alexander of Württemberg and when his patron died in 1738, the Württemberg Estates scapegoated Süss for the Duke's debts (which also had the effect of making the Duke independent of the Estates), stripped him of his offices, and hanged Süss and displayed his body in an iron cage.

As Süss's fate indicates, even successful Jews lived a precarious life in the post-Westphalian period. Toleration, if given at all, was often begrudging and could always be revoked. Despite the growing social and economic connections between gentiles and Jews, there were legal and nonlegal walls preventing full integration. The various antisemitic measures and violence indicates the wisdom of the old rabbinic adage, "if you're afraid of forgetting you're a Jew, don't worry, a gentile will always remind you." Although the French Revolution and Napoleonic period abolished various restrictions against Jews, this was much more of a paper emancipation than an accomplished fact both in central Europe and France. Repeal of various emancipation decrees was one of the first priorities of the Restoration governments and actual legal emancipation for Jews only gained ground in the mid-nineteenth century. By that time, the gradual entwining process between gentiles and Jews was coming into fruition, but the vestiges of various antisemitic tropes also remained and found new currency with biological racism.

Sources

Birnbaum, Pierre, and Ira Katznelson. Paths of Emancipation: Jews, States, and Citizenship. Princeton: Princeton University Press, 2014.

Elon, Amos. The Pity of It All: A History of the Jews in Germany, 1743-1933. New York: Metropolitan Books, 2002.

Kaplan, Marion. Jewish Daily Life in Germany, 1618–1945. Oxford: Oxford University Press, 2005.

Whaley, Joachim. Germany and the Holy Roman Empire. Volume 2. Oxford: Oxford University Press, 2012.