if I pronounce Van Gogh with a soft German/Dutch "ch"

It's interesting that you pair the German and Dutch pronunciation of "ch" - they can be very different things indeed. A close friend of mine comes from Scheveningen, a Dutch town whose name was used by the Dutch Resistance to weed out German spies, as native German speakers could almost never get the sound right, pronouncing it in the German manner, rather than the much more throaty Dutch. The sound varies considerably from region to region among the Dutch. When I was first taught the Dutch word "gek" meaning crazy, it was by a Flemish speaker, who pronounced the guttural "g" almost as "h" so, when I tried to say "I am crazy" to some Dutch friends, they thought I was saying "I am gate" - and then kindly schooled me in the tricky art of mastering Dutch gutturalisms.