Were ghosts real or were they just projection?

In The Outsider series, the main antagonist is a malevolent entity called "El Cuco" – a shapeshifter evil being that feeds on children and the negative emotions. We also know that he can project his image, like when he appears in Anderson’s house, trying to intimidate the detective to drop the case against him.
But every time when he shows up, he is in his current shape: either as his last scapegoat or as the disfigured man in a hoodie.

But then we have a few unexplained "ghosts":

• Jack is beaten by his dead mother
• Ralph is visited by his dead son, who asks him to "let him go"
• Again, Ralph sees two dead kids in a cave

If the first case one can explain as an obvious El Cuco’s ploy (he is trying to get better control on Jack), the other ones are harder to explain, especially the last one, since it is an obvious sign

So were those real ghosts or just the effect of El Cuco’s power?

I’ve only watched the series, but answers from the book are welcome.