Galarian Moltres is said to consume the souls of anything its flame touch, turning any victims into burnt out shadows of themselves aswell as having an overwhelming sinister aura to it.
Galarian Articuno can just immobilize targets and cut through steel.
And Galarian Zapdos makes the sound of electricity from its wings rubbing together and can run at 180 MPH.
This is literally the ONLY info given on them in the Pokedex. There is nothing legendary about the other two aside from them being endangered.
by Opposite_Jump_5041