Not sure if this is significant… but that’s what a blog is for, right?

Paul, a slave of Christ Jesus, called to be an apostle, set apart for the gospel of God, which he promised beforehand through his prophets in the holy Scriptures, concerning his Son, who was descended from David according to the flesh and was declared to be the Son of God in power according to the Spirit of holiness by his resurrection from the dead, Jesus Christ our Lord, through whom we have received grace and apostleship to bring about the obedience of faith for the sake of his name among all the nations, including you who are called to belong to Jesus Christ

Paul says he is first a slave because all Christians must be slaves. And he has received first grace because we all need and receive grace. Not all are called to be apostles. So he mentions that second in each instance.