This are simply called digraphs, the same as spanish “ll”

That’s actually a fun fact :D. I do wish Polish would adopt this signs though, just so we wouldn’t have these digraphs

The T turning into C is called somehow, I don’t remember how, but it’s used quite often. For example, “expensive” and “more expensive” would be “drogo” and “drożej”. I think there were even some tables for all the transformations, but I might misremember things

Our C is reffered in IPA as joined “TS” sound, so there is definitely some merit to that

I wonder if we had ž etc like Czechs would it make it easier for foreigners to read

Exit polls in Poland are usually pretty close to the final result