As Artobans Ghost clearly states I'm the head honcho here *cough*
The Empire cannon is only in AoS in the so called Compendium Warscrolls, they aren't updated into the current line, but the Dwarf cannon is. Anyway the Empire cannon can still be used through those compendium warscrolls. So now that's out of the way..
PS: Both the Empire Cannon and Dwarf Cannon bar the range are similar.
It only has one main attack type as it's named on the warscroll: Cannon Ball, there is another but it's listed as a special ability.
Aiming, and bounces is from the past edition (Warhammer 8th) so forget those. Same with the templates, maybe there is one used somewhere in AoS as a rarity, but certainly not for a cannon at least.
So how does a cannon in AoS work?
First any warscroll with a * somewhere in the profile then it will be mentioned in a "unit damage table. Monsters and Artillery have them.
So the Cannon has * as move and on the Attacks and as Artoban said it has to do with the amount of crew members are around. With full (3) crew around:
you target any single model (hero or monster type is also a unit) or a unit (group of models) within the range in the profile.
at full crew you do 2 attacks on 4+ to hit (so 2 dice)
then any hits on a 2+ to wound
then if you do wound
your opponent can save with his Save stat at a -2 modifier
then if he fails 1 or even 2 of those then you can throw another dice (the d6 damage) and see how much (damage)wounds he takes, which he might save any of them again if he has any special saves.
So you could do nothing (fail your to hits / to wounds, he makes his saves) or if your dice gods are with you a maximum of 12 damage or you could then roll a 1 for your damage.. dice gods are fickle