Kracow is nice, Warsaw is big. The best are the small towns and cities which weren’t leveled in WWII. I suggest a tour bus guide thru the country. The old abandoned pre-WWII villages are surreal. Ask to visit some. Auschwitz is creepy but worth the visit. Hopefully it’s still authentic. They had a way of displaying these huge photos positioned so that when you looked at them they were looking back on where you were standing. I went in June, late 70s when it was still a COMBLOC country.
One of my favorite sites was The St. John the Baptist Church in the town of Orawka, near the Slovak border. Poland has many wonderful old wooden churches.