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I preferr to not use plugins and rather hardcode everything into the theme, it may dramatically improve your website speed. Altough it does depend on your HTML/PHP/CSS skills.

I do however use the following on some of my websites:

Analytics 360 - Great when connected to Google Analytics, you no longer have to go there for the basic data.

All in one SEO - Fairly common used plugin, there may be better ones but i does offer some good customization.

I am currently using Wordpress and am looking for php examples on how to find interlink suggestions from other posts/tags/categories while writing. Do you know of any?

Always welcome, if you are running a mailchimp campaign, it will combine both data into 1 graphic. So you can see on your traffic stats when you have done a blog post or did an e-mail campaign, very helpfull!