SharePoint permission for Adobe Acrobat Sign integration - site or tenant level

Hi, 

I am currently stting up Adobe Sign on one of our SharePoint sites as described here:
https://helpx.adobe.com/de/sign/using/microsoft-sharepoint-installation-guide.html
Could somebody please help me with the following questions about the authentication against SharePoint

1. If I understand it correctly, there are two possibilites of authenticating: At site level and at tenant level.
Could you please explain me the difference? Is it because if I want to have more control over the SharePoint Sites on which the Acrobat Sign SharePoint Site can be used I have two choose site level or what is the reason for using site level connection if I can authenticate for every site by using just tenant level connection?

2. If I authenticate at site level against SharePoint Site with my admin user and revoke all permissions to the site from my admin user after everything is set up because confidential data is stored on the site, will the Adobe Sign App stopp working after a while?
I have tested it but it continued to work, but I did not make a test over a long time period.
If yes, could I come around this with tenant level authentication?
Or should I use a technical service account for this usecase (if my admin user should not have permission on the SharePoint Site over a long time)?

Kind regards

Marco