Understood, thanks . I was getting confused with the office 2019 and previos versions and how it relates to E3 or E5. So bottomline ,all 2019 previois versions are mutually exclusive and E3,E5 all are using pro plus which is latest.
Office 2019 is intended to On-premises instalations and customers that does not have any cloud licenses and need to be updated to the lastest on-premises Office with updates more slower that Office 365 ProPlus but as a prepetual license or in some cases in a contract with Microsoft called Enterprise Agreement. Then Office 365 ProPlus is the Office that is updated Monthly with new features and in a model of subscription.