Multiplayer confuses me.

So I’ve played the Series since the first game. And I love the fast paced Samurai shenanigans. But when it comes to the intricacies I’m very much so a noob.

What is the difference in scaling with the different forms of multiplayer? And why is there a difference?

When I Do expeditions with another player our damage seems like it just tickling the enemy(Mainly bosses), yet when I use a Cup to summon a visitor.. damage seems normal.