Wiki of Godhead in Christianity says:
Godhead (or godhood), is the divinity or substance (ousia) of the Christian God, the substantial impersonal being of God, as opposed to the individual persons or hypostases of the Trinity; in other words, the Godhead refers to the "what" of God, and God refers to the "who" of God"
From what I understand, in vaishnavite theology, the ultimate reality is a person.