Can all Question Submitters submit the questions of a Question Drafter?

No. A Question Drafter has to assign the question to one of the Question Submitters. Only this Question Submitter will be able to submit the question to the Answer Group. 

Also, it is not possible to change the chosen/selected Question Submitter when the question is already assigned. If the chosen/selected Question Submitter is unavailable, our advice is to ask the question again.