If you can't legally choose a mode because all three have been chosen that turn, that instance of the ability is removed from the stack with no effect
Neither of these options is good and one is actively bad in most cases
I know its disappointing to lose your C-Sphinx when there could be shenanigans like you and someone else both having them, but you can see how everyone else in the game might not enjoy that quite so much
It's still early enough to buy into some undervalued pieces for those of us who are inclined to do so
1 Alela, Artful Provocateur The sheer power behind Alela, Artful Provocateur is absolutely huge, with two strong abilities that synergize with each other
I've written at length about the products under that umbrella, and I recommend people give that format a try as well, if they wish to