Soft Edges is a feature of NprTools which lets you soften the edge display of SketchUp models.
Here is a SketchUp model displayed in SketchUp without edge lines
Note - the detail of some of the railings at the top is lost without edge lines.
Here is the same model with SketchUp edge lines turned on.
The edge lines bring out the detail which are lost with no edges.
However, for some applications, these edges may be too harsh.
Using Soft Edges, here is the model with the edges 50% transparent.
Using Soft Edges, here is the model with a 50% pattern mask applied to the edges.
This same concept works with Sketchy Edges as well.
Here is the Model in SketchUp with Sketchy Edges (Very harsh)
Here is the Soft Edges display with both 50% masking and 50% transparency.
Here is a blown-up detail of one of the windows showing the pattern and transparency of the edges.
You can use edge color in SketchUp to lighten the color of the edges. However using transparency and masking will help preserve some of the detail, especially when the edge lines are very close together.
The differences are subtle, but take a look at the blow up of the stairs from the 4 images. The transparency and masking is able to preserve more of the detail of the stairs.