In the Frozen Throne undead campaign, Mission 3, The Dark Lady. A special, stronger Banshee named Sharlindra is present; she was not present in the original Reforged, but as far as I can tell, was added in 1.33, and is still present today!
That's not only the case. I believe that in a missions where you have a stronger version of unit with its unique name (only possible when playing on Reforged graphics), those old changes from 1.33 were still left intact in 2.0. Notable examples were:
1.Falric, Marwyn, and Luc Valonforth being playable on the last chapter of "The Scourge of Lordaeron" campaign.
I believe that those Human Captains are also playable on the other 3 chapters of that campaign (Human03, Human07, Human08).
2.On Act 2 of "The Founding of Durotar" campaign, there's a wounded Stonemaul Ogre named Crol'ka that talks to Rexxar for the main quest, which is to find Kor'gall. Also, four Stonemaul Ogres accompanying Kor'gall will have their unique names from WoW (Ogg'marr, Tharg, Do'gol, Draz'Zlib).
EDIT: It appears that Luc Valonforth remained with 2.0. patch during the last chapter of Human campaign.
I also noticed that in "Twilight of the Gods", there are 2 notable changes that I believe was purged by the time 1.36/2.0 came out (not mentioning the ability to build the Chimeras):
1.In Jaina's base, there's a unique Human Captain unit named "Halford Wyrmbane".
2.In Thrall's base, Naz'grel and Gar'thok, two Orcish warriors you normally encountered during Act 1 of "The Founding of Durotar" campaign, can be seen aiding Thrall.
I can't provide a full detail about notable changes since I haven't played Reforged campaigns just yet, as did the original ROC/TFT ones in ages.