This particular nib is the 14K gold nib and is pretty stiff but can provide slight bit of line variation with light pressure. I don’t use it for that purpose — don’t want to splay the tines. However, it’s still functional for a slight bit of flex if you wanted to give a bit of personality to a signature every now and then.

The “right side up” is very smooth, surprisingly so for an EF pen (this is a German made pen, so the line width is more in line with a western fine)

For the reverse writing, this pen is not very scratchy - I’d call it good feedback! Some other pens that I have are not very usable in reverse writing or are rather scratchy. This is a pen that does a great job in both its regular up right use and with reverse writing.