If you're looking for a lightweight, fast and customizable WordPress theme, then both the Shema and GeneratePress themes are great options.
Both themes are built on the same foundation - the WordPress Customizer - so they offer similar options in terms of customization. However, there are some key differences between the two.
The Shema theme is designed specifically for speed and performance. It includes features such as lazy loading images and a minified CSS file to help your website load as quickly as possible. It's also optimized for Google PageSpeed Insights.
GeneratePress, on the other hand, is designed for both speed and flexibility. It includes a drag-and-drop page builder tool that makes it easy to customize your website without having to code anything yourself. It also has a built-in SEO module that helps you optimize your site for search engines.