hätte ich angenommen, dass bei meist aus dem Dt. stammenden Namen mit "sch" der andersartige Klang erwähnungsbedürftig sei
I think that in general Americans would assume that "sch" in names is pronounced ʃ. Then again, I come from the Upper Midwest, where the percentage of Americans with German heritage is high, above 40% in many areas. Look at this U.S. Census map if you want to see what I mean: https://www.census.gov/newsroom/stories/2017/...
I have known Americans with names of German origin that had non-English consonant clusters, and the "sch" was still pronounced ʃ. Some names I can think of off the top of my head with ʃ: Schaefer, Schilling, Schlenker, Schmelter, Schneider, Schrock, Schroeder, Schwink, Schweikert. In my experience, though, the Ws usually are pronounced like an American W.
I once volunteered for a senate campaign in Iowa, and I hated having to call people with names of German origin. The main reason was the vowels. Schroeder? You know it's not going to be Schröder, but if you choose the logical (from an English perspective) Schroh-der, then it will surely be Schray-der. Koenig? Should that be Koh-nig, Key-nig, or Kay-nig? As for IE/EI in names, the pronunciation cannot be predicted. As Norbert said, you have to learn the pronunciation individually. I have a student right now whose name should be pronounced to rhyme with German Wien, but it rhymes with Wayne instead. Another problem is the -ch at the end of names. Koch? That could be pronounced like Cook, Koke, or Kotch.