The first sentence is correct....but the second sentence needs a bit more explaining because being powerful is an attribute of God...but I understand what you mean by shortening it to God is power. However power is not God.
We use the word grace as in saying, God is grace or when speaking about love...God is love. Grace is an attribute of God, in connection in what He did for us on the cross and in what that action is still doing for us today. However, grace is not God, it is an attribute of God.
Calvinists seem to want to say that even grace itself has attributes. How can an attribute have attributes? Grace is not the 4th part/person of the Trinity.