Hi Peter-
Thanks for reaching out, and for using the Venetian WordPress Theme.
The Templates you see in the Page Attributes section are hard-coded into the theme. The Home template features the large call-to-action area, while the Default template doesn’t have that. You may be interested to check out the layouts available in the Add Block library, which is full of hundreds of pre-defined page section layouts.
You can remove the extra space below your header with a quick Custom CSS rule. Navigate to Customize > Advanced > Custom JS & CSS, then paste this line into your Custom Theme CSS field:
#content { margin-top: 0px; }