They are real. The beginning of the game, the soul of verso, and even Renoir acknowledge how real they are. Just because they were created by a God doesn't make them not real. Many think we are created by a God. Is it ok to wipe us out on a whim? If the Lumierians don't count as real people, having two endings makes no sense. The fact that Renoir had to make a cruel choice is because he will prioritize his family over the people of the canvas. How many parents would burn the world to save their child? Renoir is no different. And we have no reason to believe the people she brings bak aren't the same, as Lune and Sciel came back just the same without missing a beat, wondering wth just happened. Saying they wouldn't be the same is just speculation.
If God created us and Jesus decided to live amongst us, and God decided we had to go because staying on Earth would kill Jesus, would you go "You know what? That's cool. We gotta make sure Jesus can move on with life"? Hell no! You'd rage against fate. You'd try to fight however you could, which is exactly what the people of the canvas did. The Lumierians lived, loved, died, had hopes and dreams, could kill themselves, question their existence, and everything else a sapient does. I play RPGs to fight the gods, not put their well being over the common man. Make no mistake, the Dessendres are Gods, and their creations are very real. I feel like calling them not real is a way to cope with the cruelty of Verso's ending. Both endings mean bad things for some, I just prefer the option where the gods suffer vs the common man reaching oblivion.