An Inquisitorial Chimera should follow the same rules as a Guard one, but there's some dispute. For example, a Guard Chimera is amphibious, but an Inquisitorial one doesn't have that rule. The Firepoints rule works the same though.
One model may fire one weapon from the top hatch, but will count as moving (if the Chimera moves, if not, he's stationary). If a model shoots out the top hatch, the Chimera counts as open-topped for the purposes of resolving shooting in your enemy's turn (so no shooting out the top and then assaulting from the Chimera, it counts as open topped for shooting only [DARN!]).
In addition, there are six hull lasguns, which may be fired by the passangers. Unfortunately, they are mounted lasguns, which means that they can only fire to one side of the vehicle (three to the left, three to the right). It also means that Stormies shooting those lasguns shoot lasguns, not hellguns.