Justin Tadlock

X3P0: Authors is a block that lets you display a simple list of post authors for your site. This is especially useful if you’re coming over from using a classic WordPress theme and need a block that’s similar to the old <code>wp_list_authors()</code> template tag.
Aside from the full array of normal block design tools, the block lets you choose from several options:
<ul>
<li>Number: Decide the number of authors to list.</li>
<li>Order By: Choose from a variety of fields to order the list by.</li>
<li>Order: Whether to display the list in ascending or descending order.</li>
<li>Has Published Posts: Whether to only show authors who have published posts.</li>
<li>Show Feed Link: Whether to show an icon linked to the author’s RSS feed.</li>
<li>Show Post Count: Whether to display the author’s published post count.</li>
</ul>
You can find the full source code for this plugin via its <a href="https://github.com/x3p0-dev/x3p0-authors" rel="nofollow ugc">GitHub repository</a>.

Authors List Block

A customizable authors list block that lets you showcase post authors, their feed links, and post counts.

flocsy

Authors Widget shows the list or cloud of the authors, with the number of posts, link to RSS feed next to their name, avatar. It is useful in a multi-author blog, where you want to have the list in the sidemenu. 
The widget can also display an “Author Cloud” if <a href="https://wordpress.org/extend/plugins/seo-tag-cloud/" rel="ugc">SEO Tag Cloud plugin</a> is installed.

Authors Widget

Authors Widget shows the list or cloud of the authors in the sidemenu.

Authors List Block vs Authors Widget