Chief: Zamriel, Seraph of Steel has an interesting design, because she encourages you to equip multiple different creatures so they can all be indestructible during your turn
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.)
If you discard an Energy card from your hand, use Radiant Greninjas Concealed Cards ability and draw 2 more cards
By cutting some of the burn spells youd normally see in RUG or UR Counterburn decks, this frees up some space for cards like Shatter and Mana Drain, which are often absent in RUG (or Arabian Aggro, as some people call it, which is a bit too generic)