Armor negating and penetrating?

[Endoperez]

Yeah, a similar formula is used for everything.

Magical weapons add strength when there's no "str not added" tag.
Magical bows have better chance of getting a hit through shield etc, as page 77 mentions.
Spells deal the damage listed in their description, with just Farstrike and perhaps Fists of Iron adding str. The little + after damage means that having more power in the path used in the spell's casting increases damage. Exactly how much varies depending on the spell, but it's about 1-3 points/extra level or so.

[Sombre]

Just to be clear, armour negating missile attacks can still be shield parried. So long as they /are/ missile attacks and not ranged aoes, certain spells etc.

Magical bows have a better chance of getting past shield parry? I had no idea. The things you learn.