By "true path" I can only assume you mean good alignment ending or best ending in terms of saving all or as many as possible of the innocent and good people while getting rid of all the bad villains? But that's a false tag I think to call something a "true path" because it implies some canonicity or higher importance for it or implying the other paths aren't equally valid. But this is the end of this trilogy and this story...there will not be a Baldur's Gate 4 and if another BG game is made it will be a completely unrelated story with new villains, story arc, etc. So there will never likely be anything like Larian declaring any one path, ending, or set of events canon for the sake of continuity or anything of the sort.
But to go past that I also believe you are wrong about origin characters not being able to get the best good ending, whatever that might be. Sure origin characters will face different challenges but they will be able to move past them in either good or evil directions. Even the Dark Urge you can play trying to completely resist and that will lead to its own story and narrative though overcoming the dark urge is probably the most difficult because the more you resist you have to start making saving throws so if you fail that can cause issues but if you make them I'm sure that will lead to its own interesting path and story as well.
you said that the origin characters can stand aloof their destinies, because you take the place them, your soul enter the chosen origin character's body, and "help" him/her do the decisions in bg3. or they will always be locked by their deadlock, until the end of their lives.
objectively, the origin characters could be have their legends, if non-origin player character -- tav is exist and help the npc origin characters, but the npc origin characters never have the qualifications to be a true savior.
