user19249: I am using HitFilm 2017 Express to put together a few clips recorded by an iPhone (1920 x 1080 @ 29.97fps).
I see some video settings in my project tab:

When I export my video, I see even more settings - some of which are duplicated across both:

I understand that my export settings are what I actually get in the rendered file. What confuses me is the project's video settings (first picture). Why do I even have them? How do they relate to and/or affect the final production?

user19140: Project settings determine the way your source media will be interpreted (played/processed/pre-rendered) by your NLE application.
Export settings determine the format of the file that you are going to output once the edit is finished.
For example:

You shoot video on a Panasonic HVX camera in Apple ProRes 422 codec
  (HQ). Then you import the clips into your project. The project codec
  will be Apple ProRes 422 (HQ).
You plan to publish the video on youtube. There is no practical sense
  in keeping the quality as high as Apple ProRes for web delivery, so
  you choose to compress the resulting video into H.264 codec inside an
  MP4 container (listed as Youtube 1080pHD) to make it easier to upload,
  without significantly sacrificing its quality.


19249: <p>I am using HitFilm 2017 Express to put together a few clips recorded by an iPhone (1920 x 1080 @ 29.97fps).</p>

<p>I see some video settings in my <strong>project tab</strong>:</p>

<p><a href="https://i.stack.imgur.com/woQv6.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/woQv6.png" alt="Proejct video settings"></a></p>

<p>When I <strong>export</strong> my video, I see even more settings - some of which are duplicated across both:</p>

<p><a href="https://i.stack.imgur.com/bzoCv.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/bzoCv.png" alt="enter image description here"></a></p>

<p>I understand that my export settings are what I actually get in the rendered file. What confuses me is the project's video settings (first picture). Why do I even have them? How do they relate to and/or affect the final production?</p>
 19140: <p><strong>Project</strong> settings determine the way your source media will be interpreted (played/processed/pre-rendered) by your NLE application.</p>

<p><strong>Export</strong> settings determine the format of the file that you are going to output once the edit is finished.</p>

<p>For example:</p>

<blockquote>
  <p>You shoot video on a Panasonic HVX camera in Apple ProRes 422 codec
  (HQ). Then you import the clips into your project. The project codec
  will be Apple ProRes 422 (HQ).</p>
  
  <p>You plan to publish the video on youtube. There is no practical sense
  in keeping the quality as high as Apple ProRes for web delivery, so
  you choose to compress the resulting video into H.264 codec inside an
  MP4 container (listed as Youtube 1080pHD) to make it easier to upload,
  without significantly sacrificing its quality.</p>
</blockquote>
