It changed with time, but the Polish nobility wasn't the ones persecuting religious minorities for the most part.
For one thing nobles took a lot of Jewish immigrants, used them as middle management (which frustrated the church, who in turn sent angry peasant mobs against Jews, which meant Jews had to work with nobility for their protection).
Also a lot of nobles weren't Catholic, especially in 1500s protestantism was very popular (about 1/3rd of nobles and majority of magnates were protestant). Only in times of Zygmunt 3 Waza who was super Catholic and introduced some discrimination it changed significantly.
In fact nobility forced kings to sign https://en.wikipedia.org/wiki/Warsaw_Confederation which banned religious persecution.
Majority of nobles from eastern parts of PLC were orthodox at first (later they polonized and switched to Catholicism mostly), and there were some Jewish and Muslim nobles (but it was very rare). They still had all the rights including voting for kings, wars and taxes.
> There's a reason why there were so many uprisings on the territory that is Ukraine today, back when it was a part of the Commonwealth
Mostly economic, but yes, there has been some religious persecution there. Especially after the attempts to create orthodox-style pope-sanctioned religion in Ukraine.