I wonder if the makers of the series even knew who Charles XII was...
The character is nothing like him. He wasn't aggressive (though he never backed down from a fight), and he never drank alcohol, and he wasn't a sadistic, spoilt brat. Riding in a horse carriage? UNTHINKABLE. He much preferred the saddle.
Also, an interesting fact, the two characters who played Charles XII and Peter I are both German. If these monarchs had ever met (they didn't, another error in the series), they would probably have spoken German, seeing as both of them were fluent in that language, but in the series they speak English (obviously, since all characters speak it).