It would probably be worth searching the forum because similar questions have been answered in a number of ways previously. I am not suggesting you’ll find a ready made answer - although you might - but more likely you find something that will help create exactly what you want.
Define “so large”? Just curious. I test regularly with 10k or so drafts in a library and haven’t seen search slowdowns…so I’d be interested in exploring that, if I might be able to make some suggestions.
As far as export, lots of options. You could start with the backup files, which are JSON format internally, and include all the meta-data information about your drafts (timestamps, location data, etc.) and could be used by and external tool or AI to create separate per-draft files.
Otherwise, it’s mostly about creating an action with a “File” action step that exports the current draft the way you like, using template tags to include the data you want in the format you want, to name the files the way you want.
Once you have created an action that works the way you like, you can select all drafts and use bulk actions.