I found the answer to my original question, which was “How do I start with a blank slate?”
Solution if you want a page with a Header, complete blank space in the middle, and a Footer at the bottom… with no trace of Wordpress default nonsense.
WITHIN PRO
Go to Pro - Content
Click the + button
On the Page Template menu, select “Blank - No Container | Header, Footer”.
Give your page a name and such and click CREATE.
USING WORDPRESS DIRECTLY (more steps)
In Wordpress go to Pages.
Then “Add New” page. You can call it, for example, “Main Page”
After it’s added, click on Main Page to edit it.
Now go to the top right, just under your username, and click on the Gear Icon. Then scroll down a bit to the Page Attributes area. On the Template menu, select “Blank - No Container | Header, Footer”.
Next, in the big middle area of the screen, scroll down until you see Page Settings. There will be a label “Disable Page Title”. Make sure this is CHECKED.
Click the blue Update button in the top right to save the changes to your page.
Now go to Pro - Content, click on your Main Page. You should see a blank white page with none of the normal Wordpress stuff appearing. Now you can start building your Pro site from scratch.