So I see in your templates that some have transparent headers. They did that by adding custom css? Why can't the header be changed in SP page builder or Helix Ultimate?
Hi. I'm not Joomshaper team member.
Header is part of the Helix template. Commercial templates have their own unique features, so in some there are transparent headers.
Basic Helix Ultimate does not have this feature out of the box, so you need to use CSS to make it.
Explanation:
Let's imagine for clarity that Body has a blue background.

Header has position: relative; by default. Therefore, when you make its color transparent, you start to see the color of Body and it seems to you that nothing happens (as in reality Body has white bg color ).

In order to achieve transparency, you need to pull the header from the flow of elements. Then, everything that is below is shifted under Header.
This can be done using position: absolute;.
