Get to the slide and slide on it.
Cameras are the slow way to get coins, using the strat used in 50/20 all plushies / 50/20 60%+ power is way way faster and more skill based.
100 coins is pretty different from Fredbear% mainly because there is practically no rng, it's just being good at getting coins fast with helpy and the vent/door characters. It is actually decently challenging to do it fast. Still like Fredbear% in a way of course.
Instead of ground pounding the blocks and going into the water you can land on a bird that always appears on the top left of the screen and jump to top of the mountain.
Just put in Nightmare BB flip the camera and hop he is standing then flip it again even if he isn't standing takes the same amount of time to flash him so its less than a second.
You can die in seconds and Fredbear% is pretty close to a die%