If the copied permanent has in its mana cost, X is 0.

If the copied permanent is copying something else, then the tokens enter the battlefield as whatever that permanent copied.

Any enters-the-battlefield abilities of the copied permanent will trigger when the tokens enter the battlefield. Any "as [this permanent] enters the battlefield" or "[this permanent] enters the battlefield with" abilities of the permanent will also work.

The tokens copy exactly what was printed on the original permanent and nothing else (unless that permanent is itself copying something else; see below). They don't copy whether that permanent is tapped or untapped, whether it has any counters on it or Auras attached to it, or any non-copy effects that have changed its power, toughness, types, color, and so on.