Given the time that you have available, I suggest that you go to Drei Annen Hohnen. This is a 3 way junction station, and has the most action, with 2 trains crossing twice a day, and three trains together in the late afternoon. To get away from the crowds for lineside photography, a short walk from the station takes you into the forest, with plenty of good shots. Drei Annen Hohnen is just a junction station in the forest, with just a few local houses. There is a station buffet with indoor and outdoor seating, and a traditional German sausage stall on the main platform, so there is no need to go thirsty or Hungry.
A map of the network and downloadable timetables see
THIS PAGE on their web site.
Special trains running during August can be found on
THIS Page. These are usually hauled by 1 or 2 mallet locos with historic passenger cars.
The timetable is quite complicated and when I am going I usually prepare a list of all the arrivals and departures to make it easier to follow what is going to happen next.
There is a lot more information on the web site, but only some pages are in English.
I am sure that you will enjoy it. Please PM me if you want any further advice.
Don Newing
Derbyshire, UK