Nastu, Goku ,and Luffy are increased to the size of Galactus also their speed is increased to MFTL and their hunger is increased near endless as well but they can get fatigued. All four are separated to four corners of the universe.
Who will consume the most planets in a race/eating contest to the 'Ultimate Planet" at the center of the universe ?
Goku, Nastu, and Luffy can fully navigate through space with ease and they can also breath in space.
Galactus's size vary from time to time so he'll be big enough to hold our sun in the palm of his hand.
Also Galactus isn't locked to eating only one type of planet here "life sustainable" now he consume any planet life sustainable or not.