The term "Grand" King Ghidorah was actually around long before the dub (which admittedly I have not watched). But as far as I can tell it's just used to differentiate the character from other King Ghidorah incarnations, or even the Cretaceous incarnation in the same movie.
He has some interesting powers, but they seem to be tailored for the Rebirth of Mothra trilogy's fantasy elements. (Such as mind controlling.) But he is one of the smallest King Ghidorah incarnations. Only 11 meters taller than the GMK King Ghidorah.
"'Nostalgic' does not equal 'good,' and 'standards' does not equal 'elitism.'" "Being offended is inevitable. Living offended is your choice."