I think you mean Valdore, that more streamlined vessel we saw in NEM? Yes, those were a newer class of vessel for the Romulans to make up for their losses in the Dominion War. I think the line of reasoning was that the Warbird had always been more of a visual terror weapon rather than the most efficient battleship which is why it's so big yet gets trashed as easily as any other vessel. After that the Romulans decided to just make smaller but more lethal vessels and we get the Valdore.
I can see why they decided to change their fleet with the lessions they learned when dealing with the Dominion. The Valdore
-class must've been a direct answer to the robust Jem'Hadar scarab ships while the Scimitar
-class was a serious attempt to emulate the huge Dominion "super" cruisers that were almost as dangerous as Borg Cubes, although the original Warbird was already big to begin with despite being almost a Paper Tiger.
And I disagree Too Much Fun that the Romulans were squandered as antagonists when they were directly behind the evil schemes in "Redemption" and "Unity", they also seemed to be pulling the strings in The Undiscovered Country
. "The Neutral Zone" was a boring and patronizing episode that only introduced the Romulans in the last five fucking minutes, most other Romulan stories after that were a big improvement.