This is my understanding of the timeline:
2014 - Vinyl masters for the albums released between 1980 and 1989 sourced from original master tapes
2015 - Mastered for iTunes from the original master tapes (from
@Spaldy's video), this was then sourced for the CD reissues that came later. Entire different remaster project from what they did in 2014.
2017 - Vinyl issues for the 1990 and later albums, I believe these are sourced from the 2015 project and are identical to the CDs.
2022 - NOTB 40th anniversary vinyl released with 2015 masters.
2023/2024 - New versions of Powerslave and Somewhere in Time on vinyl use the 2015 masters and are thus a distinct master from what was initially released in 2014. AFAIK they haven't applied the same masters to any other 80s album besides these three, although I would be curious if they have quietly done this for other albums since afaik they are still in print and available to purchase new from retailers.
And yea, as Spaldy said, stuff was remastered but nothing remixed.