Evernote uses a syntax called ENML (Evernote Markup Language), but this is more akin to a HTML than say Markdown or MultiMarkdown as supported by Drafts. Though Drafts does also support HTML for previews, and technically the ENML and HTML are plain text, but most end user interactions are with it rendered.
However, as I noted above, Drafts deals only with plain text. Embedded images, sound files, etc. cannot be imported into Drafts.
You can link out to such data if it is stored somewhere else that can be accessed via URL, but that’s unlikely to be the sort of thing you want for your scenario.
Technical embedding such files as base-64 encoded data strings is probably also possible, but certainly not efficient for access and search compared to other solutions with a rich content viewer.
The Agenda app is quite different in many ways to Drafts. One of them being that it supports rich content, which is why you can view some of your rich content in it. But in a similar vein Drafts is more automatable/prgarmmable than Agenda. The apps simply have a different focus.