If a question meets the criteria for being flagged you should flag it right away, no matter what. If it's appropriate in context for the OP to be given an opportunity to edit the post into appropriate shape then that will be taken care of when the flag is handled.
If the question meets criteria for being closed, and that's the reason for the flag, remember that closing is not at all the same as deleting. Closed questions can be (and are very much encouraged to be) edited and then reopened. You shouldn't leave a close worthy question open to give it time to be edited. Being in a closed state is itself the way of allowing it to be edited while preventing low-quality answers until the editing is done.
In the case of spam, insults, abusive language, etc. it's generally safe to assume the OP isn't exactly planning to fix the issue, and it's important to get the attention of a mod ASAP.
If it's for any custom reason it's generally something that can't be fixed through just editing, which is why you're flagging it to begin with.
