Best WP Plugins for our PBN sites ? (especially to prevent Hacking)

If you are not using the XML-RPC API to post to your blogs, using some simple "Disable XML-RPC" fire and forget plugin & limiting logins (never use admin as username) will give you sufficient security without the very good but a little overloaded wordfence. Also keep in mind: Wordpress itself has some security issues, but third party plugins and themes are much worse in terms of security. Wordpress has a great community, but most programmers strictly focus on functionality only and sometimes forget the most basic security stuff, although it's clearly defined in the codex. That's unfortunately true for some very popular plugins, too.

For linkjuice, I always use https://wordpress.org/plugins/404-to-301/ Super easy to use: Select type of redirect, select redirect target (homepage or whatever internal or external page you want), optionally enable notification and logging, done. Still too many options and too much work? https://wordpress.org/plugins/all-404-redirect-to-homepage/ Install, activate, done.