There’s a few threads on the subject, here:-
https://originaltrilogy.com/topic/What-was-done-for-the-1995-THX-mastering/id/10303
https://originaltrilogy.com/topic/What-was-changed-for-1995-THX-version/id/79592
https://originaltrilogy.com/topic/1992-vs-1995-video-releases/id/4612
https://originaltrilogy.com/topic/Star-Wars-screening-with-Q-and-A-with-Lucas-tonight/id/7898
and probably more to be found if you go through the Index thread in here, the ‘Home Releases’ section in the OT Index, and also the SW Preservation Index.
Maybe some more information or links here?:-