Not quite accurate.
Oresrians were in the original Dark Wheel novella (alongside the original Elite game) as distinct from Thargoids. They were supposedly a peaceful race similar in appearance to Thargoids. As such they both will appear in some fan-fic by me and other authors.
Klaxians, however, are only present in ED lore.
Within ED, Klaxians and Oresrians have been revealed to be subsets of the generic term 'Thargoid' (so the Dark Wheel description of the Oresrians has been retconned). Also bear in mind these are human names for alien creatures. Those creatures are unlikely to use such terms themselves.
The only two books referring to the Klaxians and Oresrians are T. James' "Out of the Darkness" and my "Premonition". These are based on the lore of the game and can be considered canon in this regard. However, readers should be cautious in assuming that a statement on the Thargoids (Klaxian or Oresrian) by a character in a book is specifically correct in detail. They might be, but that character could be wrong, or lying for their own reasons. The books aren't 'pure lore', they are narratives of events in the ED universe.
Also, many of those characters are in privileged positions of knowledge, which is not available to Commanders in their ships. As such, until your ships' HUD clearly indicates "Oresrian" or "Klaxian" or something else (perhaps by some Galnet or pilots federation universal ID update or something), I think it's fair game to speculate on whether what we're seeing in game is attributable to those labels or not.
Hope that helps.
Cheers,
Drew.