Lord Nelson wrote:World War One Gold and To End All Wars are separate entities in style, substance, and rules. The former is also probably no longer supported.
Hi Mujado and welcome to the world of the best games you can find to play. You are correct about successor games versus original games. You should certainly start with the newest games. Your question made me think about this additional aspect: you have focused upon two of the most complex and engaging AGEOD games. If you are very new to computer wargaming, you may wish to look at War in America or Alea Jacta Est which are a bit less complex games using the AGEOD engine. If you have had some extended wargaming experience, España 1936 or Rise of Prussia and the Thirty Years War are a nice introduction to the more complex army, corps, division organization of AGEOD games.
If you have already dived into To End All Wars or Civil War 2, take your time, know these are complex games, enjoy being frustrated, surprised and delighted. And, if you enjoy playing others, dive into a pbem game with a player who enjoys sharing as this is the quickest way to learn these games.