I am not sure what that grey line is in the first screenshot, perhaps just an artifact of the screenshot ... there should not be any grey lines there ...
As for the gaps, there is always a healthy margins between the "top" section (intro or not), and the content that flows below it. There are not panel settings for this.
Margins WITH title/description:
Margins
without title/description:
The only way to remove natural margins, would be to add custom CSS ... You can globally remove the padding with the below CSS. Keep in mind, it will affect all pages. If you only want to remove the margin for
some pages, we would have to create a custom class instead, and you would need to assign it on a per-page basis.
main.main {
padding: 0 !important;
}