My experience is from 2022. Here are the places I parked: my hotel with designated space in Swednica; Klodzko Fortress (I can’t remember where I parked, but it was not problematic); Jawor Peace Church (easy); Ksaiz Castle (easy, designated parking); Jasna Gorna (easy designated free parking - donation requested).
In 2023, I went to Zalipie (no parking issues that day); then I hit 5 of the wooden churches, which all had free roadside parking. The only place I hit crowds was at an unplanned stop in Niedzica, a charming lakeside town, on a Sunday (parking was available and easy to understand - I just had to backtrack some to get to an open lot).
I almost always search for parking ahead of time and mark it on my Google maps - then use that as the destination for my directions. I just didn’t find rural Poland difficult to find parking. Hope that helps!