[Suicide Junkie]

The Fleet's strategy will determine which vehicles do what.

Once they have broken formation, they should proceed on the strategy defined for that particular class of ship.

If you want kamikaze ships to break formation and warships to stay, then make them into two separate fleets.
Shift-Click the two fleets, and tell them to attack: they will move and fight together for the next game turn. If you want them to continue to move together after that, clear their orders (if any), and shift-click, give orders them again.