The F100 is a great tool for this.
Fast modern lenses that can talk to the camera used as close to wide open as you can will help as will reasonably fast films. These two raise the quality of the overal exposure because it makes it easier to get background exposure/detail, which is being lit by ambient light and keep the shutter speed up in a reasonable range. The flash can light the main subject regardless as long as it is in the range indicated by the SB-800.
Actually diffusers won't help here, with the SB-800 in Matrix TTL MODE the camera will read the lens and measure the distance to the focus point and focus the flash to match the lens focal length. As the shutter is pushed the camera reads the background and subject and balances the exposure.
Diffusers get in the way here, they defeat the fancy math the camera does by screwing up what the flash unit can deliver to the subject.