[dreambeat]

I would go with a Kobo Clara (either HD or 2E). The Sage and Libra are both very nice, but there's not enough of a difference that I'd recommend either over the Clara for a basic first ereader, especially as they tend to be significantly more expensive. I tend to think of them as more "upgrade" options.

As to the page turn buttons - no, I don't think they're as big a deal as some people make them sound, especially if you don't have a years-long history of using them. It's just personal preference. If you're used to a touchscreen phone or a tablet, you shouldn't have any issues with a touchscreen-only ereader.

A Kobo will be able to read epub files without any need for conversion (though you can use Calibre to change them to kepubs if you decide to). Kobos also have a lot of good built-in support for sorting your books in different ways, which is nice for a large library.

EDIT: misread your post asking about buttons on the Sage to be about buttons on ereaders in general. Oops.