Example 2. Would recurring credits on a Cyberfeeder or Lockpick be lost when Nasir Meidan encounters an ICE that has just been rezzed? Recurring credits do not count as being in the credit pool and cannot be lost like credits in your credit pool.
When is a variable chosen for a card in which that variable is not defined by the card itself?When deciding X, is it decided by the effect including X or is it decided by choosing an X and then resolving the effect with X in it? 2a. The variable is chosen whenever it is necessary to resolve the effect. So for Vamp, you do not have to set the value of X until the run is successful. For Psychographics, you have to set the value when playing it because it is part of the cost. So option 1 is correct.
2b. X is a value that is set at one time. So you spend X credits from Vamp, but you cannot spend more credits than you have. With Power Shutdown, you trash X cards from your deck, but you do not see the cards that are trashed until X is defined. You cannot trash more than the number of cards in your deck, either.