Melkor- that's what I was referring to when I was saying that was not what Daemora meant, if you believe that interpretation. GL's own comments about the creation of the Sith involve no race of any sort. The whole point of this is that there is so much contradiction and so many continuity issues in the whole Sith origins thing that the best approach is to call it all myth and for people to take what they want from it.
As for the rest...
Unfortunately a lot of these ancient names have absolutely no link to the modern day- the names either fell into disuse or translation issues mean that their modern day versions remain unknown.
Metephia, however, is known. In fact it was a known Sith world in their original invasion of the Republic. However, the Metaphian faction that dominated Sith politics for many generations was (and is) long gone. The Thrid war ended in their submission and their importance gradually faded to the point where their existence did also. Metephia ia just a far out world with a history that it was once the headquarters world of a Sith faction; nothing more.
The Third War- not to be seen as a single confllict or even a set of conflicts, but really an ongoing time period in which many things occured (more like the Punic or Peloponessian wars in history)- spanned much of Sith space as it existed at the time and most planet,s under the thrall of some Sith bigwig (this all predates the use of the term 'Darth'😉 took one side or another- and in typical Sith fashion, and another and another and another...
And although this is a broad simplifcation of a complex area, the main power blocks in the end were the Metaphians and their allies on one side, and a coalation opposed to them on the other. The strongest of this opposing coalition was a faction called the Kasmanae (another group that Daemora identifies as a cultural subset of an overall 'race' of Sith). The final 'act' of the Third War was a series of campaigns as the Kasmanae sought to destroy the worlds allied to the Metaphians.