Will Scrivener substitute for Final Draft?

I know that there is a screenplay mode, but can Scrivener put a screenplay into draft format for submission, or would I still need to purchase Final Draft to clean a document up for submission?

Yes. Scrivener does produce a presentable first draft, definitely.

If it comes into a development stage or production, you might have to migrate the project to a dedicated screenwriting package like Fade In or in the worst case scenario Final Draft.

If you have to be precise with page count, then you’ll need to open the compiled output in Final Draft or a fully compatible program. Scrivener does its best to approximate page sizes and appearances in script writing mode, but it’s not designed as a page layout program, so words may wrap to the next line in FD that didn’t in Scrivener (or vice-versa). The same with the last line on a given page; sometimes a line may end up on the next page in one program but not the other.

Why “in the worst case”? I really like Final Draft.

I’ve used FD and don’t really like it. It feels clunky and cludgy, like it was written 30 years ago and never caught up with changes in UI design.

Scrivener feels incomplete as a screenwriting tool.

So, IMHO, neither is really suited to the task.

Final Draft is really inferior, old technology that crashes. In addition, it’s overpriced.

There are many better options available for free or less than $50.

Free: WriterDuet
Paid: Fade In Pro ($50)

You could stop there and be happy.

If you’re interested in writing in Fountain, Highland and Slugline are good choices.
Afterwriting.com is also excellent, free and you can sync to Google Docs or Dropbox.

I’ve found Scrivener great for outlining, planning and writing in Fountain, but all the heavy lifting is much more pleasurable and accurate in Fade In Pro.

Final Draft preys on new writers saying it’s the industry standard and if you want to use what the pros use, use Final Draft. This is horsesh*t. More and more people have been so fed up with Final Draft, they’ve moved on to better and more modern software. The industry standard is PDF.