For Forms you can run query as "SELECT * FROM [dbo].[cf_bp_steps] where definition_json like '%{emailaddress}%' "with your Forms database( replace {emailaddress}" with the email address you want to search.

For Workflow, you could start from the mail server side. In the Workflow Admin Console, under External Objects, right-click on the mail server and go to View Linked Workflows. That will give you a list of which workflows to check. You can either export them as XML like you suggested, or you can open them in the Designer and do a search for activities of type "Email" in all open workflows. If you go with the Designer search, you can then double-click the search hits to go directly to that activity and updated as needed.