1.Signing a form is little more than formality.

I know the sentence can be changeable like the following below.

2.Signing a form is only formality.

But can I change the first sentence into others like the followings below, and Is the meaning also all the same?(with number 3,4)

3.Signing a form isn’t much more than formality.

4.Signing a form isn’t much more than signing a form is formality.

Lastly, I want to know the part of speech of the word “more” in all sentences above.