Timo Schlueter

TagMeta generates meta keywords using your most used tags. 
It automatically gets the 10 most used tags out of your 
blog posts and pages and puts them into a valid meta- 
keyword string. This string then appears in the header of 
the home page of your theme. If you want to add tags per 
post, i suggest youre going to use the Headspace plugin.

TagMeta

TagMeta generates meta keywords using your most used tags.

xenice

Xenice SEO is a simple, fast, and lightweight SEO plugin designed to give you precise control over meta descriptions and keywords for every post, page, and taxonomy.
Unlike heavy SEO frameworks, Xenice SEO focuses on the essentials — helping search engines better understand your content without slowing down your website.

Xenice SEO

A lightweight SEO plugin that allows you to add meta description and keywords fields for posts, pages, categories, and custom post types.

TagMeta vs Xenice SEO