My friend and I had a HUGE argument over this, he gets very very pissed off if you disagree with him.
Anyways, the process of miscast says resolve the spell, apparently to him that doesnt just mean the spell, it means all remains in play that effect it. I brought up the point that if 2 items clash or do the same thing, or 2 spells etc, the book says "the controlling player decides" ie, you choose what to use.
But, If you were to not use throne of vines, you would have to voluntarily dispel throne, as part of the spell is to ignore miscasts on a 2+ ( apparently)
Its very edgy tbh, I always used to play I choose what I want to use, and keep throne regardless, but after the hissy fit I conceded.
At the same time, I would have to agree that you would most likely have to get rid of throne to use cupped hands, and roll on the table, as you dont even see the miscast before you choose to roll it away with throne. So you couldnt cherry pick when to use cupped hands :/
A very very strange issue