For the difficulty bit, there is decks you can make that hit consistently really hard. The only issue is that they're very similar because there's only one draw engine atm. Always include K.C, Mana Jackpot, and ARC helpers and then always include the beanie outfit. If you want to make it pretty op, use the pengi hoodie and hot pants and I promise everything becomes really easy. If you include all of that you can pretty much make the deck whatever you want. Other than for Syd, I don't recommend going over 35 cards. It's starts getting a bit too inconsistent.
Edit: The helper cards include 3 of each.