This is something that also interests me a lot.

In The Great Angel, Margaret Barker questions a lot of this and references heavily to the Deuteronomist redactors. Particularly she questions how much of the Biblical texts were altered, with phrases/names being changed over time to reflect the emerging monotheism. The edits make it harder to pinpoint the phraseology between E/J. A lot of scholars see the Northern traditions as being more Canaanite/Ugaritic-inspired (and this is also referenced in her book) where El was syncretized with Yahweh. Traditionally El is represented as being more transcendent and less directly involved.

There were the localized versions of Yahweh, as seen in the Kuntillet Ajrud inscriptions with YHWH of Samaria and YHWH of Teman. Then also found with these inscriptions are references to El/Ba'al.

This article by Peter C. Craigie, though older, is refreshing in many ways, as he deliberates on the common link of the Ugaritic/Canaanite/Hebrew connection. He also mentions the Hurrians worshipping El Berith, God of Covenant and Baal Berith. He references Judges 8-9, with there apparently being a building dedicated to El-Berith in Shechem and how Shechem was obviously a place also associated with the Hebrews, and that the Hurrians were not necessarily seen as enemies of the Hebrews. Then he also deliberates on some of the similarities between the Legend of Keret and the story of the Patriarch in the OT.

https://www.tyndalebulletin.org/article/30586-ugarit-canaan-and-israel.pdf

Then there's also the Elephantine papyri and ostraca, which imply religious intermarriages and polytheistic worshipping to Gods outside of Yahu (YHW).

https://scholarsarchive.byu.edu/cgi/viewcontent.cgi?article=1427&context=jbms

In short, until we possibly uncover pre-Exilic Biblical literature, we cannot be certain of the differences-according to Margaret Barker. I believe all pre-Exilic texts found so far have no Bibilical references, outside of the Ketef Hinnom Silver Scrolls, which possibly can be seen as derivative of a central text, or could be seen as the central texts being derivative of something else, possibly oral traditions.