OK, that's two clear votes so far. Thank you.
In case anyone is interested, here are two websites that have a version of the Romulan War that seems to be compatible enough with TOS and TNG canon that I tend to use them as inspiration for the era, even if specific details will certainly be different:
History of the Earth-Romulan War at Star Trek Minutiae, and the
Starfleet Museum. With the latter, it helps that a lot of the Romulan War-era spacecraft look like they can be written up in three sections, for compatibility with GURPS Spaceships.