Show mouse region preview

Here you can activate the mouse preview (when the cursor is hovered over a surface, its Radius will be displayed).

Show Placements

Here you can activate the display of the placement radii (based on the Bounding Box + Object Spacing) as red circles.

Show Splat Regions

This option is the one you can most readily disable. If you scatter using a negative Object Spacing value and a disabled Use Splats option, the Viewport will be flooded with white circles, which is not desired in most cases. Otherwise you can read here, how the splat region is defined.