I think the vine of the 3 of Coins acts as a kind of Cup (more a florid chalice), eching the cups, a vessel for one of the Coins, enclosing it while the King of Swords passively reflects on how to release it.
In the 2 of Cups, the cups are open, releasing, like lips! It isn't done by force though, it isn't the Knight. The mood is contemplative, the Sword poised not thrusting. I think this is definitely to do with enclosing and releasing (something; an idea? an opinion? A person?) and how best to do it.
Why does the contrast between the 3 of Coins and the 2 of Cups makes me think of the contrast between keeping silent (enclosing vine) and opening up (open vessels)?