Max Puliero shows us a cool feature in Blender in this tutorial: Realtime outline for a cartoon character which is a mustsee in my opinion.
Max uses the Solidify Modifier and Backface Culling for the shading to get this nice effect of outlining for a toon character:
These are the options you have to use to create the outline effect in the viewport.
A nodesetup for toonshading is also shown in the tutorial:
but that is actually created by the youtuber Light BWK which is also woth following.