If all of Brigid's Command's targets are illegal as it tries to resolve, it will do nothing. If at least one target is still legal, it will resolve and do as much as it can.

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

If the copied permanent is a token, the token that's created copies the original characteristics of that token as stated by the effect that created that token.

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

The token created by the first mode of Brigid's Command copies exactly what was printed on the original permanent and nothing else (unless that permanent is copying something else or is a token; see below). It doesn't copy whether that permanent is tapped or untapped, whether it has any counters on it or Auras and Equipment attached to it, or any non-copy effects that have changed its power, toughness, types, color, and so on.

If the copied permanent is copying something else, then the token enters as whatever that permanent copied.