This translation of the Ethiopic Book of Enoch varies significantly from the scrolls only in organizational structure, with an attempt at making it into a “pentateuch” ... tetrateuch, honestly. There is some evidence in certain fragments of translation from Greek rather than the original Aramaic, or Hebrew in the instance of the Noah traditions. I've seen no indications that the translation itself is in any way faulty.
The Slavonic is far more sketchy. There is even a purported 3 Enoch. There are those who claim that the entire New Testament has its ultimate foundation in Enochian themes and thought.
Outside of the commentary, dating analysis and the actual, physical authentication provided by the Dead Sea Scroll fragments that are themselves analyzed, I just don't see any outstanding difference, myself.
Here is a link with several knowledgeable individuals, including Charlesworth, discussing 1 Enoch and other writings, that may be of interest:
As you have explained, Enoch I, II and III are completely different types of manuscripts - Ethiopic, Slavic and Hebrew. The content is very much different.
The E.Isaac translation of I Enoch in Charlesworth's "Pseudepigrapha" uses as a primary text "the fifteenth-century Ethiopic manuscript found in a monastery in Kebran, in Lake Tana." He continually compared that manuscript with a late eighteenth century one found in the Garrett collection at Princeton University and with the text of R.H. Charles. He followed the latter two when the primary text was obviously wrong or unintelligible. He also compared the primary text with existing Greek fragments (Akhmim, Syncellus, Greek papyrus as edited by Bonner.) The Qumran fragments were also consulted.
The commentary and footnotes explain the differences between the manuscripts, context, relationship to Scripture, etc.
Previously on this forum I have bothered to type in large segments of the Isaac translation to compare to the Laurence translation which is readily available on the web so that posters can see the difference. It takes a lot of time and I'd rather not have to do it again to make my point.
As I recall, one occasion was a crevo debate when the correspondent demanded modern day evidence supporting fulfilled prophecy.
To make a long story short, scholars proceed under the presumption that prophecy is impossible. Thus the older web translation (I believe it was Laurence's) included a footnote remarking a certain passage was clearly referring to Herod and that therefore I Enoch had to have been written after he lived.
Of course that translation was before fragments of a copy of Enoch were discovered in the Dead Sea Scrolls. Some of the astronomy related fragments were carbon dated (as I recall) to around 200 BC.