While The Flash will be a similar multiversal epic to Marvel's Spider-Man: No Way Home, the upcoming DC movie from Warner Bros. will have much larger and far-reaching consequences. Mirroring the Flashpoint event from the original comics, Barry Allen will attempt to save his mother in the past, an act which inadvertently changes the entire timeline and leads to a collision of worlds within the DC multiverse. As such, the circumstances of The Flash will lead to a far more significant ending than No Way Home's.
https://screenrant.com/flash-movie-multiverse-ending-no-way-home-different/