Do I need to install a caching plugin on wordpress sites?

Question

caching

Initially, for a dedicated server (low cost), optimization was ordered from systemintegra. The server is running on centos 7, nginx + apache + php 5.6 in fastcgi + opcache mode. There are 7 wordpress sites on the server.
And now I’m thinking whether it’s necessary to install caching plugins on each site in addition to this (for example, WP Super Cache, inspired by the post habrahabr.ru/company/regru/blog/263781/).

Answer 1

1. It is necessary. But you must have Memcached or Redis installed on your server. They will give a very noticeable increase.
2. Optimization was done to you very "so-so". Firstly, there is no mention of caching backends (see paragraph 1), and secondly, "optimization", in which Apache is present, is not such. Apache is one of the bottlenecks for low cost / low end servers. Everything Apache does, Nginx does, only orders of magnitude faster.

Answer 2

Necessarily. The effect is noticeable to the naked eye on almost any type of site. Especially in online stores

Answer 3

Certainly. WordPress caching plugins significantly increase website speed

Answer 4

I support Igor. Remove Apache, install and configure Nginx + Memcached + caching plugin + Minimize JS CSS CSS and the site will fly anywhere