When you look at the design screen for ships you will notice on the second page of the information screen (see attached pic) that it gives you the total Hull Structure. So that line is saying target all weapons until you have enough to possibly inflict more than 200% damage to the structure points of the target. Note that Hull Structure is not the same as Tonnage Used although the two could end up with the same values.
The AI would continue to use the default strategies but the only way you could use them would be to start a new game. To play it safe I would leave the default ones though. Not so much for the AI's benefit as for you as you work on fine tuning the ones you want; think templates.
