The Simple Answer

To a Complex Historical Question:

“How to determine who is the true authority in Greek & Doctrine from the Earliest Church Period?”

Simple:

“Let’s ask the” Father of Church History” himself, Eusebius of Caesarea who wrote ‘Ecclesiastical History’ and note who he mentions as the foremost authorities in doctrine & Greek (both person & region; even endorsed by the Bishops from the regions where the Gospel was born: Caesarea, Jerusalem, Samaria) whilst noting also who he named as the heretics (E.g. the Gnostics).

Guess what? The best of the Christian Universalists are celebrated in his writing to be the successors of the Apostles of the Lord (“apostolic seed”) such as Clement of Alexandria, Origen of Alexandria etc.”

P/S:

Please go and read it for yourself:

https://www.google.com/url?sa=t&source=web&rct=j&url=http://www.documentacatholicaomnia.eu/03d/0265-0339,_Eusebius_Caesariensis,_Church_History,_EN.pdf&ved=0ahUKEwiJ7YrFrIHQAhULro8KHaWQBzwQFggbMAA&usg=AFQjCNFnAe0asaF-Y_VGJGa8agZcVBVbRQ&sig2=_O9Mnyf-_5RR-y8M2UCVlA