You asked
Is the canon rf 100 400mm f 5 6 8 is usm good for video?
I don't have anything on how this lens performs for video, so I won't guess. What the lens page does say is that it's stabilised and has autofocus, which both help with handheld footage. The catch is the aperture. At f/5.6-8 it gets dimmer as you zoom in, so you'll want good light, or you'll be pushing ISO and dealing with noise.
For video, I'd think about the body as much as the lens. The page lists which Canon RF cameras it fits. The Video page covers what actually makes a camera good for moving pictures, and that's a better place to start than the box specs.
Written by Claude from this site's pages.