What is the best way to align header & contents of a website

I'm working on a Ecommerce website which consists of a landing page, product search page and a details page designs. I got struck with the header alignment design. So, I tried to refer a lot of websites where there are different types of headers as in the following screenshots where they use headers with both fluid containers and normal containers. And there is also a different combination on page content containers with respect to header containers.

What is the best practice and there is any specific reason behind the header and content alignment? should different kind of webpages like a landing page, blog and other pages should have different kind of headers and content alignments?

The following screenshots were taken from 1600x900 resolution screen monitor.

Fluid header and Fluid content

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http://www.flaticon.com/

Fluid header and normal content

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https://www.google.co.in/search?num=20&q=user+experience

Normal header and Normal content

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http://www.creativebloq.com/

Normal header and Fluid content

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https://www.pexels.com/