Scanline Classic has presets for VGA and higher resolutions. I recommend either vga.slangp, svga.slangp, or xga2.slangp for VGA games. The higher resolutions have a stronger scanline effect.
For Hercules you’ll need one of the many monochrome presets which I haven’t finished yet. However you will find an example monochrome preset in the demo folder labeled ‘TheMatrix.slangp’. You can also use bwtv but that wouldn’t be period accurate.
For EGA you can use any of the NTSC presets or a VGA preset as VGA was compatible with EGA and RGB CGA.
For CGA composite you’ll need to use an NTSC preset with the appropriate composite emulation. I think DOSBox supports this in the emulator so you wouldn’t need to add an NTSC modulation shader but I’m not sure.
Note that VGA is only compatible with EGA and RGB CGA (NOT composite). EGA was compatible with CGA. Hercules wasn’t compatible with any of these (it was for monochrome, business monitors). You won’t find a shader that can accurately simulate all of them at once.