What is the difference between Office 365 Business Essentials and Office 365 Enterprise F1? According to this sheet, the only difference is in Exchange Online: Office 365 Business Essential includes Exchange Online Plan 1. Office 365 Enterprise F1 includes Exchange Online Kiosk. On the product page, it says "Included is a 2 GB per user mailbox […]".
I never heard of Kiosk Mode. What are the differences to a Exchange Online 1, besides the mailbox quota?
Kiosk is for deskless users, i.e. people that will primary use Office 365 on a mobile device. It does not include the desktop applications, and even if you get them separately, you will not be able to configure such mailbox in Outlook via Exchange mode. It will only be available via POP/IMAP or ActiveSync on the mobiles. In addition, you get the lesser storage and some other restrictions, here's a detailed comparison: https://technet.microsoft.com/en-us/library/exchange-online-service-description.aspx