If this can handle those sites where every section is behind an accordion that must be expanded (and especially where it collapses other sections when you expand one), then this is going to be awesome.
It extract the main content using Readability by default (you can configure it with something else). Logins would depend on how you're parsing. It has two modes, it either browses to the page inside the window (for non-refreshing pages), or retrieves it in the background using fetch.