There are three things that affect strategy. You and your opponents/teammates, the setup, and the dice.
Because there is no affect of dice G1 for instance, the only factors are you and the setup. This comes down to the fact that the setup offers some moves and you pick the best one.
It depends on whether you’re talking about OOB or Alpha. In OOB, kamikaze may be used if the ships end their combat movement in a kamikaze zone, whether or not there is a battle. In Alpha, kamikaze are triggered by combat, not combat movement, so the ships must actually fight in a kamikaze zone (or launch an amphibious assault from it) in order to be targeted.