As for the design, Negan does something I quite enjoy: he creates a mini-game where players can try to psych each other out
Thats a strong fit in decks that care about tokens and populate effects and that have a nice changeling or doctor in the 99
Unfortunately, the way Mathas is worded is that only counters placed by his ability will trigger the card draw, but Bounty Hunter can still snipe any creature with a bounty counter including the ones placed by Mathas
Note that this is a 6-part podcast on LE
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.)
Goreclaw, Terror of Qal Sisma Without Surrak, Goreclaw cares less about your little guys and more about your big guys hitting harder