Plugins
There are thousands of plugins you can install on your site that perform all manner of functions.
Good plugins have a very light touch and will not affect performance. The problem is many do the opposite and can slow down a website.
You shouldn’t need any plugins to add features to this theme.
But it’s a good idea to install a security plugin like WordFence as this will help protect your site. And if you have enabled comments you will need Akismet. It’s not free but well worth the effort.
But try to avoid anything else. In particular don’t use a page builder.