Mulligans
General Mulligans
You have 10 one-drops-- mulligan to them. Your card advantage engines of Secret Passage and Greyheart Sage will come down the road to re-fill and re-fire your bullets.
Keep an eye out for absurd Edwin keeps, especially on the draw where you can keep [1-drop, Shadowstep, Edwin, X] and just play a 8/8+ on turn 2.
Almost Never Keep: Questing, Sap, Eviscerate, Galakrond, Secret Passage, Shadowstep (without an obvious combo draw).
Tempo-Aggro with a focus on Secret Passage card advantage that goes back to hand at EoT.
Galakrond is just there for Praise Galakrond! to increase Intrepid Initiate spellburst activations; sometimes wins grindy games with Lackey spam vs control.
Sap effects are some of the most important cards in the format right now, basically have to be playing two until meta shifts away from Druid / Paladin / Priest etc.
Explosive combo draws necessary (Edwin, Questing) for the aggro decks to compete with the huge idiots and big swings of the likes of Druid, Mage, Paladin, Warlock, etc.
Stealth package got really insane with the new 3/1 replacing Skyvateer, a lot more consistent aggressive Greyheart Sage draws.