My answer is based on personal opinion and observation, and please take it for what it is: an over-generalized way of making a point. I will start with color, than physical structure, and finally, temperment differences.
Here's what I can tell you. The working line dogs, whether East German (DDR) or West German come in coat colors of Black and Tan, and Sable and Pure Black. Black and Tan ,Black Sable,Tan Sable
,Brown Sable,Dark Brown Sable,
Now, Sable is a rich color. Very rarely if ever at all
, will you find a dog from a workng bloodline that is Black and Red
...and that would indicate a show bloodline
. So one of the easiest ways to tell if a puppy is from a non-working blood line is if you have a Black and Red puppy or dog.
Some colors that meant by these words can be seen on this website: http://leerburg.com/pupcolor.htm
In general, the East German DDR dogs are thicker boned and have a deeper chest that their West German Counterparts. In general they show more "bone" and have a flatter top, closer to the dogs of the 1920's and 1940's. It's sometime in the 1960's and 1970's that the show lines and working lines started separating so much. Prior to that, there wasn't much of a difference. In my personal opinion, West German Working bloodlines show a "roached" back, whereas the East German and Czeck dogs show a more straighter back. The "roached back" is kind of the exact opposite of the over angulated back on the American Show line dogs. Here's a good photo of a Roached back:
A good photo differences between East German and West German Working lines can be seen on this link:
that shows the differences quite well.
In general the Czeck bloodline is descended from the DDR bloodline, but in my opinion, show more defense drive than prey drive. In other words, the ideal "sport dog" that can do Schutzhund protection work is about 70% prey drive and 30% defense drive, or about 60%/40%. However, this dog is "prey object oriented" meaning, if they don't see a bite sleeve, they might not react in a real world situation. However, a dog that has more defense drive might be a better personal protection dog and not as good in the Schutzhund world. The breeding program of the Czeck dogs was very, very heavily influenced by one man: Mr. Jiri Novotny. He ran the Border Patrol program and it's his "vision" of producing dogs for government used, in a government owned kennel that can be said to product what is today's Czeck bloodline. These dogs are 60% defense and 40% prey the opposite of the West German line, speaking in general terms. They have higher built-in aggression.
In my opinion, the Czeck dogs are not for the novice handler. They have pronounced fight drive, and have higher level of defense drive. However, if you are looking for a police dog, that can do real world police work, this would be the ideal line. If however, you are looking for a pet dog, this is too much dog for the average handler.
So the goal of a breeding program and the goal of the handler are very important to understand. The goals of the Czeck breeding program was not to produce pet quality dogs, but dogs suitable for police or military duty.