What software do you use?

Autocad Civil 3D (2017-2019), Infraworks and 3DS Max.

What file formats can I expect my work to delivered In? .

Dwg/.Dxf/.Pdf/.xml/.avi/.mp4 are the most common. Many more are supported through the Autodesk software.

Can you stamp and sign documents?

Because I'm a drafter and designer only, you would have to get a registered engineer or surveyor In your state to stamp and sign your documents.