“Chara is awake and present in neutral/pacifist as well as NM“ is, from what I can tell at this point, 99% likely to be canon, judging from all the hints and clues people have dug up thus far. It’s hard to think of an alternate explanation for the combined factors of Flowey’s message at the end of True Pacifist about resetting being addressed to the first fallen human (and explicitly NOT to Frisk, who Flowey now recognizes as a separate individual – “Let Frisk live their life”), the SAVE file being in the name of the first fallen human, the “but nobody came“ music on the load/reset screen for a True Reset, and the flashbacks to the first fallen child’s fall and death (sneakily introduced long before the player has the context to know what they’re actually seeing and reading) littered throughout the game.
The remaining 1% in that guesstimate represents “the creator has not explicitly confirmed this, in what TVTropes would call ‘Word of God,’ in totally unambiguous language.” And, welI… I don’t think Toby will ever explicitly confirm it, since it’s clear he was really intent on obfuscating the full extent of the first fallen child’s presence in the game.
“Chara is the narrator“ is more technically arguable, I admit, but it makes sense in light of “Chara is awake and present in all routes“ as an explanation for odd aspects of the narration that can’t just be brushed off as “It’s a quirky rpg with a quirky sense of humor.“