Mulligans
General Mulligans
Hard mulligan for your 1 and 2 cost minions. If you're going second and already have Acornbearer or Cable Rat, keep Whispering Woods. Bees is worth keeping if you already have your turn 1 and turn 2 plays.
Control Mulligans
Wrath can be a good answer to Warrior's Eternium Rover, especially in conjunction with Keeper Stelladris, but don't keep it unless you already have at least one 1 or 2 cost minion. Whispering Woods can bait out early game board clear, leaving you free to flood the board with more powerful minions from your hand.