Also, is Queen Wanda a well-known figure in Polish Culture today?
Yes, she's a symbol.
The problem with Polish history dating before late 10. century is quite simple - no written sources, very weak presence in Roman or Byzantine historiography. The earliest existing annals (chronicles) of Poland were written in the 12. century, and like many medieval or antic writings they mix factual truth with beliefs and legends making it hard to decide which of described events were real, which were myths and which were partially real.
So by today's standard we may say that Krak (Wanda's father) was a mythical figure, because he slayed a dragon, in which we don't believe, but maybe it wasn't a dragon, but some other animal, or maybe dragons did exist :)