Hi Scott,
Answering your qustions:
- You can override any of the Publii pages by editing the source code of the theme files e.g. index.hbs https://getpublii.com/dev/theme-overrides/
In addition, you can create multiple posts and tag templates, and then assign them to any tag or post. https://getpublii.com/dev/how-to-create-custom-templates/
- Instead Agolia, you can use built-in Google Custom Search
- Pictures and videos are displayed into a post in the normal way:

- You can create as many menu levels as you like and it will look like:

- Publii does not offer breadcrumb functionality, but there is a way to create it, what I describe here https://publii.ticksy.com//ticket/2110215/
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