DAT files are used by point products, ePO is just the repository to host them for the endpoint to retrieve them.
To answer your question which DAT files do I need? You need to know what products you have, and which DAT file type they use.
VSE uses v2 DAT.
Thanks, how about Engine Updates? Is epo5700eng.zip the beta release or ready for production?
You would only find beta code on the Beta page of the website.
What you find on the DAT and Engine download page are production releases.
You might want to be mindful of whether the package is an elective download vs. automatic download, where the latter is added to our Update site and the former is not. It's still a production release, either way.