G'raha Tia's last ability resolves before the spell that caused it to trigger
If you stick solely to Vampire Aristocrats like the precon promotes then I think Clavileno and Carmen are about the same power level where it boils down your own preferences and your own meta: Clavileno is cheaper and provides a slow but consistent payoff, whereas Carmen is more expensive but also more explosive and randomly becomes more powerful if you happen to play against decks that sacrifice a lot (fetchlands, treasures, other Aristocrats etc.)
They preferred instead to spend all of their parents' money so that they could walk around holding as many cards as they could in one hand, with seven Charizards on the top of their deck
That being said, theres a bit of a flavor mismatch here, as The Endsinger is more destructive than counter-focused, but thats not the end of the world
If a spell or ability targets multiple things, you can't target it with Untimely Malfunction's second mode, even if all but one of those targets have become illegal