Hi Hans, Thanks for your question here on Q&A.
To start as I read: "Can you please guide us on Azure AD Sync settings" - do you so refer to the migration of the settings for Azure AD Connect (Renamed to Entra ID Connect) or?
Ref.: https://learn.microsoft.com/en-us/entra/identity/hybrid/connect/how-to-connect-import-export-config
Just to be sure in your question :)
Regarding #4 - is there an On-Prem Exchange Server?
Let me hear from you :)