Megaman is a VERY supportive character in teams, and functions very differently from his 1v1 matchups. He ABSOLUTELY needs a character he can heavily support with his projectiles while the other does WAY more damage, although megaman is also very potent with his kill moves in most matchups.
Characters he is great with:
C. Falcon, Sonic, Little Mac, etc.
Basically fast and powerful characters who can quickly deal the damage while megaman is off to the side
(also villager, because pocket is AMAZING)
Characters he is terrible with:
Projectile campers (although the links aren't too bad)
Playing as the megaman:
Stay off to the side and if approached use grabs and other attacks and quickly retreat
Playing against the megaman:
KILL HIM FIRST
Have a member of your team focus SOLELY on him, and if villager is on your team, you can completely remove his metal blades/crash bombers by pocketing and taking the item out of pocket and putting it back in (doesn't work with crash bomber, throw it before the thirty second timer goes away). Megaman can only have one of any of his projectiles on the field at a time, so he can't throw the metal blade AT ALL, which destroys his strategy.
Hope this helps!