The line width is regulated by the pressure on the pen when you write and the tip is durable, so don't be afraid to press down when you want thicker lines. On the black fudenosuke, you have the option of choosing between soft or hard tip and there is not a crazy big difference between them. Many people who have used the pencils for a long time notice an immediate difference, but for the vast majority it is a little hard to decide which one to use.
The black Fudenosuke have a water-based pigment ink that is waterproof. Thus does not bleed through on paper (obviously depends on the paper as well). In recent years, it has also come in colored versions that look like chalk on a blackboard, wonderful. And not to forget that they are also available in standard traditional colours.
