i have no answer for your first question, but for your second, well, the names pretty much explain their function.
FS2OGGcutscenespack.vp adds cutscenes in OGG format, multi-mission-pack.vp has the multiplayer missions, you need that pack so you don't end up downloading the missions from the host, multi-voice-pack.vp adds voice acting for several of those multiplayer missions, completely optional, but recommended.
here be a link to the multi missions
And Here be the cutscenes.
Uhm, the large textures one, i'm not sure it does anything... specially if you are using the mvps, best way to find out is to check by yourself Edit: fixed linkage