I’m no expert on the grain side, but Netflix had a nice writeup about its power.

netflixtechblog.com/av1-scale-film-grain-synthesi…

I also heard that when you use film grain, but disable the denoising done on the output to properly preserve detail in the encoding. Which depends on the encoder, but should generally be possible on the ones that do film grain.

But it might not be as good for artistic film grain that doesn’t fit normal “grain” in videos.