Does Grace stack with existing dodge chance? What about Aspects?

Does Grace simply set a creature’s dodge to 30%, ignoring said creature’s Speed and Dodge stats entirely? Or is it a second dodge chance, rolled in addition to the normal dodge chance?

Does a Summer Aspect’s dodge rate decrease when it gains Grace (from 50% to 30%)? Does it ignore Grace in favor of its default 50% dodge chance?

Do the Aspect traits cause their respective creatures to ignore their Speed and Dodge stats for calculating dodges?