Add guide for choosing one Classic UI theme or another, thanks to @je…

…nsens!

docs/classic-ui/theming/index.md

@@ -13,13 +13,41 @@ myst:
 
 This section of the documentation describes how to theme Classic UI.
 
-Small theme changes—such as the site logo and favicon and minimal CSS changes—can be made by {doc}`changing theme settings through the web <settings-ttw>`.
-Other theming methods should be used for larger customizations or entire website designs.
-These other methods include creating an add-on, tweaking the Barceloneta theme, Diazo, and from scratch.
 
-```{todo}
-Provide more information about the other methods and why a developer should choose one versus another.
-```
+## TTW or add-on?
+
+Small theme changes—such as the site logo and favicon and minimal CSS changes—can be made by {doc}`changing theme settings through the web (TTW) <settings-ttw>`.
+This method is especially useful for short-lived or prototype sites.
+It allows you to make minor adjustments without needing to dive into code or production-level setups.
+TTW can be convenient for quick experiments, websites that don't require complex theming, or short-lived websites.
+
+An add-on allows you to keep your customization modular, and it provides a more structured approach to larger-scale theming.
+This method is ideal for more permanent or complex customizations since it enables easier maintenance and portability.
+
+The customized Barceloneta theme, creating a theme from scratch, and Diazo offer even more flexibility.
+
+Barceloneta theme
+:   Ideal for a starting point, especially if you want to tweak it as an existing, solid theme.
+    You can customize its components and styles without starting from zero.
+
+From scratch
+:   If your project requires something completely unique and none of the existing themes fit, building a theme from scratch would be the way to go.
+    This is most appropriate for highly customized websites with distinct design requirements.
+
+Diazo
+:   Diazo can be used where designers create a self-contained HTML page with CSS and JavaScript without customizing templates.
+    It can be used for simple themes or for more advanced methods.
+
+    Its advantages include allowing more complex themes where content needs to remain flexible, and you want full control over the markup.
+
+    Its disadvantages include a possible negative performance impact from the rendering process, and a more complex and difficult to maintain theme.
+
+To summarize:
+
+-   Use {doc}`TTW <settings-ttw>` for minor changes or testing.
+-   Use {doc}`add-ons <create-add-on>` for production-level theming that needs scalability, maintainability, and modularity to customize Barceloneta or to write themes from scratch.
+-   Use {doc}`Diazo <diazo>` in your add-on if you need to modify the markup without touching the page templates.
+
 
 ## How-to guides