Mulligans
General Mulligans
Early drops for early game, and according to Hearthstone Replay, Dr Boom is among the highest win-rate card in the archetype, so I would recommend keeping him if he decides to grace your opening hand.
Aggro Mulligans
These are simply the cards that help you survive aggro. You can try to keep other cards as well, such as shield slam and brawl, but often they can be inconsistent depending on the aggro deck you face, and how well you know how to use them. Supercollider is very valuable against aggro, but keeping it in the opening hand is almost impossible because not only do people often play around it, but if you draw the second you now have at least one dead Supercollider in your hand.
– 2 weapons project
+ 2 execute