If you mark a RT-field Pass-Thru HTML (add a space before and after, Text -> Pass-Thru HTML), you can fill it with HTML through formula.
You are limited to ~64k of data per field, and you will have to experiment a little with the generation of the HTML-string (using an array/implode), as Domino tends to give this error-message: HTTP Web Server: Lotus Notes Exception - The formula has exceeded the maximum allowable memory usage.
The advantage with WQO compared to setting the HTML in "Default value"/using a computed text is that you can move the code out of the form (I prefer as little as possible code in the form). You can run multiple agents on WQO if you have several RT-fields you want to fill (menu, maincontent, etc).
When generating HTML, I've been using more and more Evaluates inside LS-WQO-agents. In some cases, where the generated html is less than 64k, formula-agents may be the best "tool".
>> Demo-db with different formula-agents running by @UrlQueryString/a form with two formula WQO-agents.