Filmic maps the scene dynamic range to the display dynamic range. It’s not artistic, it’s technical : “white” on the scene may be 1600 times brighter than “white” on your screen, so we need a not-too-destructive way to convert the dynamic range (and gamut) between media.
Since this conversion usually involves compressing tones quite a lot (aka flattening the contrast), the filmic contrast slider is provided for damage control, to restore contrast around mid-tones. Think of it as a mitigation operation. It’s not artistic.
Color balance RGB contrast is meant only as a shortcut to quickly change the contrast of masked parts when used with masks (for example : enhance the foreground). It should not be used globally as it changes the apparent dynamic range of the picture and triggers circular editings when filmic is already set.
For artistic contrast, use tone equalizer.