Settings
The Settings group contains a single button that lets you set optional properties for the Glow and Smokelet particle types in Form. The settings dialog is opened using the Settings button below the custom preview control, as seen here:

When clicked the Settings dialog appears:

There are two control areas in the Settings dialog, Glow and Smokelet settings. These controls change the rendering qualities of the built-in Glow, Star and Smokelet particle types and cannot be animated.
Glow
The Glow group settings are only active when the particle type is Glow Sphere or Star.
The
Glow Size controls sets the relative size of the glow compared to the particle size. For example, a particle size of 2 and a glow size percent of 300 will make the particles glow be 9 pixels in diameter around the particle making each particle cover 11 pixels in total.
Opacity simply controls the opacity of the glow area separate from the particle.
Feather controls the edge softness or falloff of the glow. High value create heavy softness while low value create a solid area around the particle.
Transfer Mode controls the compositing of the glow area with options for Normal, Add and Screen modes. These work the same as the Particle Transfer Mode control but change just the glow.
Smokelet Shadow
The Smokelet Settings are only active when particle type is set to Smokelet.
The
RGB values set the color of the shadow where each smokelet is drawn. The default value sets the shadow to a dark gray value but by changing the values you can lighten or darken the shadow, specifying color values of 0-255 for the Red, Green and Blue channels.
Color Strength sets the blend percentage of the shadow color specified above with the orginal particle color set in the Particle Color control.
Opacity is the opacity of the shadow, with higher values causing dark shadows and lower values causing brighter or non-existent shadows. A value of 0 will make the smokelet look flat and featureless.
Light Name lets you specify a light object from the current After Effect's composition that will be used to control the location of the shadow. The name in the text entry should match the name of the Light layer in After Effects. The light type can be a point or parallel light.