Writing workshops and peer review sessions can be incredibly beneficial for improving a draft. The most accurate option from your list is:
They give you a chance to find out how your draft actually affects readers.
These sessions provide an opportunity to receive feedback from peers, allowing you to understand how your writing is perceived and interpreted. You can discover areas that may be confusing, impactful, or need more development, which can help you make informed revisions to enhance your work.
While workshops can occasionally lead to the exchange of ideas and suggestions that might inspire revisions, their primary value lies in the insights gained about reader reactions and perspectives.