Pull the plain text out of an EPUB, chapter by chapter - here in this tab, with nothing uploaded.
Text is what you need for notes, a word count or a screen reader. It is extracted here in the tab and the book stays on your computer.
In reading order - the book's spine - with each chapter's title above it if you like.
No: a .txt file is plain text only. For formatting, use EPUB to Word.
Only if they have no DRM. Copy-protected books are encrypted, and removing that is not something this site does. Books from Project Gutenberg, Standard Ebooks, Humble Bundle and most indie stores are DRM-free.