Nested IA Structure - What's the best way to get it set up?
Lots of question so I'll describe how I would do it more or less. Ask if you want more info.

/ - single page type.

/about - single page type.

/industries - single page type.

/about/{slug} - structure page type (structure offers nested entries)

/industries/{slug} - structure page type

You cannot create /about entry within structure with slug like /about/{slug} - thats why /about is a seperate single page type page.
Of course you can create single structure with {slug} as url - then /about and /industries could be created within structure section. Note: with many entries it is harder to handle in CP.

About structure would have following entry types:


bios
contentPage
contactForm


CP Section edit screen


CP Entries:

about/_entry template would look like this:

{% extends "base_template" %}
{% block body %}
    {% switch entry.type %}
        {% case "bios" %}
            {% include "about/bios" %}
        {% case "contentPage" %}
            {% include "about/content_page" %}
        {% case "contactForm" %}
            {% include "about/contact_form" %}
    {% endswitch %}
{% endblock %}


or it could be (but I prefer first approach)

{% extends "base_template" %}
{% block body %}
    {% include "about/" ~ entry.type %} (filename == entry type)
{% endblock %}


Channel/structure sections can have multiple entry types. All of them use template defined by Entry Template - thats why we include other templates based on entry type.

/about, /industries single page template:

To fetch data from all subpages you can either hardcode it to fetch entries from section like this:

{%- set entries = craft.entries({
    section: 'aboutSection',
    order: 'postDate desc',
    limit: 20
}) -%}

{%- for entry in entries -%}
    &lt;h1&gt;{{ entry.title }}&lt;/h1&gt;
    //use switch to display data specific to entry type
{%- endfor -%}


Or you can add entry field (lets call it subpages) to the page and display it like this:

{%- for entry in entry.subpages -%}
    &lt;h1&gt;{{ entry.title }}&lt;/h1&gt;
    //use switch to display data specific to entry type
{%- endfor -%}


With field approach you can change content without changing the code.

Here is hybrid - use query when no entries assigned to entry field:

{%- set entries = entry.subpages %}

{% if entries.total() &lt; 1 %}
    {%- set entries = craft.entries({
        section: 'aboutSection',
        order: 'postDate desc',
        limit: 20
    }) -%}
{% endif %}

{%- for entry in entries -%}
    &lt;h1&gt;{{ entry.title }}&lt;/h1&gt;
    //use switch to display data specific to entry type
{%- endfor -%}


Similar industries section:

CP Section create page


CP Entries:


UPDATE

Industries Overview entry type template

Here you could query items like so:

{%- set entries = entry.chrildren -%}
{%- set entries = entry.chrildren.descendantDist(n) -%} n levels below entry
{%- set entries = entry.chrildren.type('content') -%} specific type of children
{%- set entries = entry.chrildren.type('content').with(['field', 'field']) -%} .with() helps reduce SQL queries


.children returns ElementCriteriaModel same as craft.entries so all methods here apply.

Or again you can add entry field and display specific children.

UPDATE 2

Q: In the case of the Medical > Portfolio being a single entry type WITHIN a structure, I'm assuming individual Portfolio Items would be housed within a Channel of their own?



Yes, that is one approach. To achieve this you would create a new section with URLs disabled (unless you want portfolio items to be accessible via URL - ex. separate page) like so:



Then you just query those items. Oh, I used Stucture instead of Channel - in addition to nested entries, Structure allows to reorder entries.

{% switch entry.type %}
    {% case "medicalPortfolio" %}
        {%- set entries = craft.entries.section('medicalPortfolioItemsSection') -%}
        {% include "industries/portfolio" with {"entries": entries} %}
        ...
{% endswitch %}


Important thing here is to create additional entry type per industry so you can query proper portfolio items. Also new section per industry. It is not good solution here because we duplicate things.



Another way is to use Matrix field to define portfolio item. This way you just use Portfolio entry type with Matrix field within Industries structure.