This article has major spoilers for Oblivion's Dark Brotherhood quest line. Yes, this is a warning for a nineteen-year-old spoiler.
Oblivion Remastered is a very faithful recreation of Oblivion. The two games are far closer aligned than anyone would have imagined during the rumour-laden months preceding the game's surprise release. That's because, for the most part, Oblivion Remastered is just Oblivion with a new coat of paint; the original Creation Engine is literally running beneath a veneer of Unreal Engine 5.
That's why we have all the same bugs and quirks that we had nineteen years ago. However, Virtous did change a couple of features in the remaster. The levelling system has been revamped because the old one was obtuse and nonsensical even back then. You can no longer go first-person on horseback, but that could be changing in the near future.
However, a user whose name I dare not repeat highlighted another change in a recent Reddit post. People who played the original Oblivion, or have been diving deep into Oblivion Remastered, will know the big twist of the Dark Brotherhood quest line, where Lucien Lachance is framed as a traitor and murdered by the...