The token copies exactly what was printed on the creature and nothing else (unless that creature was copying something else or was a token; see below). It doesn’t copy whether that creature was tapped or untapped, whether it had any counters on it or Auras and/or Equipment attached to it, or any non-copy effects that changed its power, toughness, types, color, and so on.

If you return a face-down creature to its owner’s hand, the token will be a face-up colorless 2/2 creature with no name, no abilities, and no creature types. (The face-down creature card will be revealed to all players as it leaves the battlefield.)

If the copied creature had in its mana cost, X is 0.

If the copied creature was copying something else, the token enters the battlefield as whatever that creature was copying.

If the copied creature is a token, the token created by Supplant Form copies the original characteristics of that token as stated by the effect that put it onto the battlefield.

Any enters-the-battlefield abilities of the copied creature will trigger when the token enters the battlefield. Any “As [this creature] enters the battlefield” or “[This creature] enters the battlefield with” abilities of the copied creature will also work.