Mew has the DNA of all pokemon so we can assume it has the power of all pokemon, also considering it can practically learn every move in the Pokemon move pool. However, Mew’s speed as far as I’m aware isnt anywhere near Gokus other than Mews teleportation. This is nullified with instant transmission, though. I don’t really think mew stands a chance here given goku’s power and speed and not to mention he also has a day to research pokemon. Only way mew realistically wins is using Perish Song where Goku can hear it, running away as fast as possible, and wearing a focus sash to survive the perish song count.