creating visual differences in colors and line weight of lines, curves, splines and etc.
SketchUp is 3D modeller, using straight edges to create (approximate) curves to form faces … a model.
The lines (edges) does not have a weight.
You need to use layout for this kind of thigs. (I’m not an expert of it).
However in a “certain level” you can give a visual distinctiveness in SketchUp for the edges. Using the styles: applying material to edges, use section, etc. … use color by tag, different dashes for tag …
( https://help.sketchup.com/en/sketchup/choosing-style ; https://help.sketchup.com/en/sketchup/applying-dashed-lines-layers; etc )