1 Corinthians 11:3. About "Headship"? A Trinitarian Heresy? No and No. Paul's point here is Oneness-unity as in Genesis 2:24 and Deuteronomy 6:4. He is preparing to quote legalistic suggestions in verses 4-6 and to refute them. Verse 3 is the platform on which he stands. There is no distinction to be made among believers in Christ. That especially means no dismissing women or demeaning them with extra regulations.
Does Head mean "boss" here? No. Does Head mean "source" here? I don't see why.
The head-body metaphor points to one-ness. It illustrates unity in Christ. See Ephesians 5:31-32 and our book Beyond Eden, Ephesians 5-6.