are this canonical events? did they really happen? or it just an other mangaka that decide this clash?
based on Ace novel which is supervised by Oda, who also did the cover and character concept arts for the novel, that's all I can say
The move Ace used is Dai Enkai: Demon Flame(onibi鬼火), which is usually used to refer to will o' wisp
This move and scene is a reference to the song the children were singing in the original
The narration here goes "Even 10 years old knows this, the pirate Whitbeard...is scarier than demons"
so you have Newgate destroying Ace's fire demons with one punch