Would someone kindly help me understand shields, stats and how they work etc., and which shield is best for thm.

Specifically, I see alot of thm's running around with bladed lantern shields. Currently I'm using just a vintage square shield, mostly because of the +3 macc. While I understand that each shield has it's own magic potency and accuracy, what I don't know is this active only while the shield is raised? Typically, as thm, I seldom ever raise my shield.

I apologize in advance for this noob question. I tried to get a better sense, exactly how this works on the gld forum, but didn't find what I was looking for.

Thanks.