Most of the interview in the desktop versions is identical to the interview in the corresponding online version. But the desktop software has additional features that are not included in the online versions.
You should enter all of your information through the interview. Doing the whole tax return in forms mode is complicated and error-prone, and deprives you of the guidance that the interview provides. The main value of forms mode is to be able to view the forms as they are created and trace the source of an amount on a form. There are a few very uncommon tax situations that are not covered in the interview and require an entry in forms mode, but those are rare.
One thing to be aware of with the desktop software is that the only copy of your tax return is on your own computer. You are responsible for backup and retention. TurboTax does not have a copy of the tax return, and cannot help you if you lose the file because of a computer malfunction, user error, or other mishaps.
