Explanation:
Box 1: Solution system settings
For Power Apps in Settings > Customizations > Customize the System you can configure email and document management, activate or deactivate processes, and more.
Box 2: Environment variable
When should Environment variables be used?
Some examples include:
When an input parameter needs to change across environments and should not be hard-coded. For example, a URL that points to a different resource in development and production environments.
If you're building a solution where your customer is required to provide an input value.
Application setup pages.
Incorrect:
A connection reference is a solution component that contains information about a connector.
Reference:
https://docs.microsoft.com/en-us/powerapps/maker/model-driven-apps/advanced-navigation
https://powerapps.microsoft.com/en-us/blog/environment-variables-available-in-preview/