Hungarians, often present in Polish military, came en masse with king Bathory and distinguished themselves throughout his Livonian War and earlier, in the war with Royal city of Gdańsk.
Lithuanian and Ruthenian horsemen belong to cavalry units known then as 'jazda kozacka' and came from the equestrian nobility of Grand Duchy of Lithuania, today Belarus and Ukraine and yes, parts of Russia. The 'jazda kozacka' also could and did include newly arrived settlers like Circassians and older populations like Polish Tatars.
..Lithuanian horseman with a lance
.. Polish horseman, perhaps a hussar retainer
.. Hungarian noble
.. typical Hungarian hussar
.. Wallachian hussar
.. another image of a Tatar
..and another Ruthenian carrying a rohatyna lance
Additionally, our Commonwealth forces also included nobles, their retainers, and mercenary warriors from German speaking parts of Poland (Poland had large population of emigrants from war-torn Holy Roman Empire) and the Holy Roman Empire (including Polish speaking Silesia and Duchy of Pomerania). During XVI century large parts of the Commonwealth dressed in the same fashions as the German states, and newly acquired Livonian states had mostly German-speaking nobility dressed as in German states, so the Germans in de Bruyn's plates should be included as well. The third installment will include these plates.
top image shows Polish noble and his retainer carrying a tuck