Can anyone help give me a tip on private persons or companies that offer excellent expertise in any of these four cities? Will be there in October.
Any of the major tour companies in Berlin will offer outstanding private tours. Many of their guides are experts in their fields, whether architecture, WW2, Cold War or Jewish history. I do recommend checking their reviews and ratings over on Trip Advisor to see the top 4 - Insider Tours, Brewers Tours, Original Tours, or Jeremy Minsberg
For Munich, I would recommend 2Dark History Tours2 for private tours. They have an excellent reputation and you will get a very individulized experience.
I have been told that "Milk and Honey" Tours is good in both Berlin and Prague. Private tours for small groups or individuals. You could google their website. We went on the Berlin Walks tour and it was good. Also The Reichstag offers small group, free tours. This is in addition to the long line of folks coming thorough the front door who probably have a tour of sorts. This small group tour is prearranged and you are let in through the north side entrance. You must email them and request a time. Visit their website. We enjoyed that tour very much and it was very nice not having to stand in the long, long line. One of my better planning details!