If the vector layers's shapes of the particle layer uses the same soft edge value for all of them and this value (blur radious) is not so big, the result is exactly the same than apliying a blur to the complete particle layer and none efect ti the shape of the vector layers. As big is the soft edge blur radious of the shape worst is the equivalence to the blur radious of the particle layer.
For example I've rendered a smoke particle (removed the flame) with the same values from original (the shaded effect was removed) And this is the result.
ORIGINAL SMOKE: RENDER TIME: 15 seconds (don't laugh!!!
)
Then I remove all the shaded edge of all the vector layer's shapes and inserted a blur radius of 20 (more or less the average of the soft edges blur values) to the particle layer. Here is the result
MODIFIED SMOKE: RENDER TIME: 8 seconds
There is noticiable difference, but it could be worse if smoke is not so important but render time is.