Create custom 401 and 403 error pages with any WordPress theme without writing a single line of code, set it up and forget it.
No not at all. You just install the plugin set it and forget it. The plugin isn't theme bound so it'll work even after switching themes.
This tells caching plugins like W3 Total Cache and WP Super Cache not to cache the 401 and 403 error pages. This does NOT affect the cacheability any other pages of your site.
No it doesn't. You have to manually edit it and add the necessary configuration specified in the plugin's option page.