It really depends what the authors of the Names wanted them to be in the first place.
In english there is a fundamental issue because most of the english last names are translatable, especially in fantasy settings, authors love to give people surnames that gives a hint of where they were born, or about their status, personality, whatever.
In the Witcher, to follow your example, i don't think many last names were in polish from the beginning, of course Geralt z Rivii was translated into Geralt of Rivia in english and Geralt de Rive in french, but that's ok, because "z Rivii" is polish, Geralt is not, and Triss Merigold was Triss Merigold in Polish, English and French. The name was never intended to be translated whatsoever, same as most of the places in the game, i'm pretty sure they were fantasy names and not Polish names.
So often europeans settings can easily be translated into english without issue because Names can't be translated in most cases, but when you translate an english setting with its boatloads of Smith, Hightower, Coldstone or whatever. You'll run into translations issues. Should you preserve the original names or translate to give foreign readers the same hints as english readers ?
As a general principle, if you're going to write a book or make a game, and expect it to be translated, don't give your places, items and characters names that can be translated if you don't want your translators to come up with awkward writing.
I think that's an important point you should consider Mr Sawyer, Cain and Avelonne