Kraków starts a southern itinerary. A city-only stay may need no car until you leave for the countryside.
The airport lists on-site rental-company desks on level +1 of the passenger terminal. Follow your supplier’s directions onward to the vehicle and confirm the return bay.
A car is useful for rural accommodation, lake districts and a route with stops beyond the main rail corridors. Warsaw, Kraków, Gdańsk and Wrocław city stays can be separated from the driving days to avoid paying for unused parking.
Compare airport collection with a later collection if you start with a city stay. Include the transport to a different rental branch and any extra parking nights when comparing the total cost.