I do not know if St. Patrick’s association with the Catholics or Baptistic people can truly be discerned after 1600+ years with only two documents composed by him.
You can find St. Patrick’s confession at http://www.ancienttexts.org/library/celtic/ctexts/p01.html.
There are five points that are significant to me. In paragraphs, 1, 26, 32, and 41 he refers to: ‘nor were we obedient to our priests’, ‘episcopate’, ‘rank of Bishop’, and ‘the daughters of the chieftains are to be seen as monks.’ I would not be surprised based on these comments that he was associated with the Catholic church.
However, in the years of his ministry, being around AD 450, the Catholic church was still in its early formative years. It was not the Catholic church we know today. It was probably more like some of our Baptist conventions and associations today. But St. Patrick does not mention any particular association with a church. In paragraph 48, he mentions ‘ for the sake of God and his Church.’ This could be a generic reference, or it could be reference to the ‘universal’ Catholic church concept that was spoken of in the First Council of Constantinople in AD 381, just 70 years before St. Patrick’s ministry.
Though St. Patrick’s church association appears to be indeterminable, his profession of faith for salvation sounds good, his confession shows fruit of the Spirit in his life, and paragraph 60 indicates to me that he believed in eternal security. These distinctives are Baptistic though denominations as we know them today were not formed yet. And because the Catholic church was in its formative years, I suspect that many churches associated with Catholicism in that day were New Testament, Baptistic churches. The inclination to centralize and unify continues to this day among many new testament churches.