SOCD stands for simultaneous opposite cardinal direction. Basically, if you press "left" and "right" at the same time or "left" while holding "right", and vise versa. Every game handles it differently ...
I've found that crt-tv-slotmask or crt-tv works best for consoles, but I tend to prefer crt-scanlines for most arcade games. I know it's less accurate, because CRTs in arcade cabinets (like any color ...