7 Wonders Duel: Age cards before or after Wonder selection?
I had a look into rules. Choosing the wonders is part of preparation of game so something done before any age starts. When you have a look on Age description it says: 


  At the beginning of each Age, shuffle the corresponding deck, then display the 
  20  cards


So for me it is quite obvious that you don't know cards when choosing a wonder as preparation of game need to be completed to start first age.

For Pantheon it is even bolded sentence:


  Perform the Wonders selection phase.


As part of setup for age one which comes after instruction to prepare cards. 

So in fact it looks order is different with addition than in main game.