As for Schindler's List depicting Polish speaking guards in the Nazi camps, almost all guards were German, and most non-Germans weren't Poles, but rather Ukrainians, or Latvians.
You are misinformed. There were many Poles who helped the Nazi's in the Nazi death camps. Usually it was a futile effort to avoid death.
Sonderkommandos were prisoners who agreed to help the Germans for better treatment. They were reviled by the other prisoners as well, even though many of the Sonderkommandos were also killed. The entire panopoly of human endeavor played out in the prisons but in grotesque fashion.
https://www.quora.com/How-did-people-in-Nazi-concentration-camps-treat-each-other
Sonderkommandos were Jews who helped the Nazis.
Also Poles, as you know.
Wikipedia admits Sonderkommandos were usually Jews.
USUALLY! Were they Polish Jews or from some other country?