Hi partner,
1. The main difference is that Sales is a Web client app and the Sales Hub is an Unified Interface app.
Only the Unified Interface app supports mobile. Most latest features are only supported by the Unified Interface app, such as 'PDF Generation'.
This is an introduction to the Unified Interface: https://docs.microsoft.com/en-us/power-platform/admin/about-unified-interface
2. As long as you have the latest Sales module application installed, you should be able to get Sales Hub.
This dose not require other additional installation or configuration.
Go to Power Platform (https://admin.powerplatform.microsoft.com/environments), then select the environment you want to work in.
Select “manage solutions” in the top menu.
Then you will go to Dynamics 365 Administration Center.
Look for and select Dynamics 365 Sales Application. If it is not installed, then you need to install it. If it is not up to date, you need to update it.
Once you have successfully installed the latest "Dynamics 365 Sales Application" solution, as in the screenshoot, you should be able to use Sales Hub and find the "PDF Generation" feature.
For the configuration steps of "PDF Generation", please refer to this document:
https://docs.microsoft.com/en-us/dynamics365/sales-enterprise/enable-pdf-generation-quote
