Goku and Vegeta have access to all the same Super Saiyan forms, but they're clearly each more adept with certain transformations.

Dragon Ball Daima surprised fans with the debut of Vegeta’s own Super Saiyan 3 form, but the penultimate episode of the ...

Seeing that there was no other option, Goku turned into Super Saiyan 3, suggesting that he was set to fight Gomah alone in the next episode.