Hi pistolpete, I agree with all or nearly all of what you posted on the other topic thread, about Paul's gospel being a different gospel. I had learned of much of that years ago. From the years of about 2000 - about 2009 (or possibly until later than 2009) I read the entire Bible (including the apocrypha), and studied the Bible, using only non-JW translations. I also studied with the aid of commentaries of 'Christendom', and evangelical books which are critical of WT teachings, and web pages promoting ex-Christian ideas. I also read and studied some of Bart Ehrman's books (I checked them out from the library). I thus knew of Paul speaking of what he called "my Gospel". What I didn't know however is that NWT instead uses the wording of "the good news I declare".
You posts at https://www.jehovahs-witness.com/topic/6221415232569344/my-gospel make an excellent case for showing that prior to the destruction of Jerusalem in 70 CE that Paul's version of Christianity competed with, and was significantly different from, the Christianity (or messianic Judaism) of the Torah keeping Jewish believers in Jesus.
Biblical scholars know there were Torah keeping Jews known as Nazarenes and those known as Ebionites who considered themselves followers of Jesus (but I am not sure if Jesus really existed as a historical person), but who also considered Paul/Saul as a false teacher and a corrupter of the teachings of Jesus the Nazarene.
I read that the Torah keeping Jews who accepted Jesus (in other words, those of the circumcision faction of Jesus' followers) nearly eventually out competed Paul's sect. But, after Jerusalem (which was the base of operations of Torah keeping followers of Jesus) fell in 70 CE and after if fell again after the defeat of the Bar Kokhba Revolt in Judea in 135 CE, the sect founded by Paul became the doctrinal victors of the early Jesus movement.
A number of atheists teaching the Christ myth theory (which I largely accept) say that the letters of Paul are the most reliable sources for determining the earliest teachings of Christianity, but I think that is primarily only the case for the Pauline sect of Christianity. I think it reveals little of the non-Pauline Torah keeping version of messianism based in belief in Jesus the Nazarene. I think the Gospels, the letter of the Hebrews, and possibly even the book of Revelation are much better sources for determining what the Torah keeping non-Pauline believers in Jesus (and gentile Greek speaking Proselytes [who at least kept the Noahide Laws] to such) believed in.
Regarding Revelation being a possible witness to non-Pauline Torah keeping Jewish believers in Jesus, see Revelation 14:12.
I suspect that most of the pre-Pauline believers in Jesus were Greek speaking (instead of predominately Hebrew or Aramaic speaking) believers in Jesus. That is partly because that which are extant of what are called the Gospel of the Hebrews, the Gospel of the Nazarenes, and the Gospel of the Ebionites are in Greek. [But all of the extant copies of these might be translations from Hebrew into Greek, or possibly even concoctions by Greek church 'fathers'.] Another reason is that a number of Christian ideas in the NT seem to be dependent upon the wording of the Greek Septuagint translation of the Hebrew scriptures.
The wording of the Septuagint in some verses allows for a larger range of interpretation of the scriptures than does the wording of the Hebrew text, and as a result allows more for some uniquely Christian interpretations of the pre-Christian Jewish scriptures. For one example, the name YHWH (Yahweh/Jehovah) becomes Kyrios (Lord) in the Greek text. Likewise the Hebrew word Elohim (which has a range of meanings, including 'angels') becomes theoús (gods) in the Greek text.