How does Gideon, Champion of Justice's ability work?
A ruling on the gatherer page for Gideon says


  Gideon, Champion of Justice's power and toughness are set to the number of loyalty counters on him when his second ability resolves. They won't change later in the turn if the number of loyalty counters on him changes.


So, he is assigned a power and toughness when the ability resolves, and it doesn't change.

If you copy Gideon in this state, the copy is just a Planeswalker. The effect that makes Gideon a creature doesn't get copied.