Don't you mean kapuśniak-style Polish soup? I think kwaśnica is mostly made in the Tatra mountains area and they use sauerkraut, pork ribs (smoked), bacon, sausage, potatoes, carrot, onion, garlic, and even mushrooms. Overall it's better than the regular kapuśniak ;)
Here an article about the difference. Both soups require sauerkraut. But kwśnica also uses sauerkraut juice, mutton and mushrooms. It must be clear soup - only potatoes and meat inside.
While kapuśniak uses other kinds of meat and contains sauerkraut farfocle, potatoes and other veg.