Combining smooth effects and blend modes with pixel art often clashes. Yet, I've played various PS1 games that make limited use of such effects (as in, not smeared over everything), and they don't seem to clash.

Is there anything different about Blend modes on the PS1? Were such effects usually dithered? Did they have stages of opacity? The only other thing I know is that it's generally going to clash if effects are rendered at a higher resolution than the pixel art, for obvious reasons.