[Arkcon]

Ganerally, for units, it's first on -- first hit. There may be some randomness though.

A shielded wp is a good idea, it at least protects the planet, but its more useful to hit back -- add some weapons to each.

There's nothing wrong with the massive planetary shield, it's just time consumeing to build for the protection it gives.

Organinc armor, IIRC, doesn't regenerate on units.

Remember, if you're playing the AI, it appears it can see the fire power you have in cargo, and will plan a fleet accordingly -- or just skip it for less defended worlds.