There is a discussion in modern scholarship on the so-called "New Perspective on Paul", that Paul wasn't necessarily antagonistic to the Jewish faith, but rather exporting aspects of its ceremonial 'purity' laws (dietary, circumcision, observances of days) on the gentile converts. The 'Judaizers' were then Jews who imposed ceremonial purity on non-Jews.
https://en.wikipedia.org/wiki/New_Perspective_on_Paul
But it's not something that I'm invested in, or deeply informed about, just adding a note here, that my perspective probably has some overlap with a wider body, with some maybe influenced by verses that have impacted my thinking.
But a perspective is just that: it's a view, based on some available information, and a personal, subjective interpretation of said information. It's not reality itself. At the end of 1 Corinthians 12, Paul writes, "And now I will show you a better way". (12:31b) My perspective isn't something to argue over, nor is anyone else's. So I try to hold my perspective lightly, lest I should lose my way.
If I've made any positive contribution to this thread, I think it was to point out that James' "royal law" seemed apace with Paul's "law of Christ" and the Fourth Gospel's "new commandment". Because of our faith in the Lord Jesus Christ, we've been transferred into a kingdom of love. And now we endeavour, through steadfast faith (his faith transferred into us as a growing seed, and now operating in us, and flourishing through good works of love expressed) to remain on the Way home to the Father.
I don't see NT authors James, John, Peter, Paul, and Luke, as operating at different spiritual levels, some 'lower and more natural' and some 'higher and more mystical'. All were holding forth the same singular reality, of the faith of Jesus Christ, and the flourishing life that follows. There is everything else, and then there is "the more excellent way".