Install and activate Meta Box and Meta Box AIO plugins.
Create this field group (JSON export) using Meta Box for your desired post type:
For the Video type field, set "Max number of files" to 1.
In the Settings tab, set the Location to your desired post type.
Step 2
Edit your Pages and populate the field for each.
Step 3
Let's create a function for use with a Dynamic Data condition to ensure that the video Section gets output only on Pages that have the field populated.
Install and activate a code snippets plugin like WPCodeBox 2.