Every believer has some theology of the atonement. Faith, after all, is trust in a crucified Saviour, and without some understanding such faith is impossible. Faith knows from the beginning who died on the cross, and it knows, too, why he died. He died for our sins.
But faith can never be content with such elementary knowledge. It wants to live its whole life at the foot of the cross, seeking with every passing day to understand it better.