In General...
https://enterprise.arcgis.com/en/server/latest/manage-data/windows/client-geodatabase-compatibility.htm
enterprise geodatabase version is primarily used by Esri Support to troubleshoot issues; it does not entirely reflect the functionality available to you, as a lot of geodatabase functionality is implemented in the clients that access the geodatabase and not in the geodatabase itself.
For enterprise geodatabases, the geodatabase version mostly only reflects what software version you used to create or upgrade the geodatabase.
https://desktop.arcgis.com/en/system-requirements/latest/databases-in-the-cloud.htm
And you only need make sure the azure sql cloud version is compat with the geodatabase.
In Reality
https://support.esri.com/en/technical-article/000017062
--->not too much to be aware of from deprecation notice
ArcGIS Enterprise 10.9.1 Issues Addressed List - Page 13 - Enterprise Geodatabase
https://downloads.esri.com/support/downloads/other_/1091-IssuesAddressedList_111921.pdf
--> there are some bug fixes for enterprise geodatabase on azure sql. It's fine.
ArcGIS Enterprise 10.9 Issues Addressed List - Page 12 - Enterprise Geodatabase
https://downloads.esri.com/support/downloads/other_/109-IssuesAddressedList-081021.pdf
--> some bug fixes for enterprise geodatabase upgrade from 10.7.1 to 10.8.1. It's fine.
ArcGIS 10.8.1 Issues Addressed List - Page 6
https://downloads.esri.com/support/downloads/other_/1081-IssuesAddressedList-072420.pdf
--> bug BUG-000126821 - Upgrading an SDE schema geodatabase to version 10.6 or later as the SDE user fails with a -37 error if the geodatabase contains feature classes with non-versioned archiving. will be an issue if someone tries to upgrade to 10.8 from >= 10.6
ArcGIS 10.8 Issues Addressed List - Page 5
https://downloads.esri.com/support/downloads/other_/108-IssuesAddressedList-02132020.pdf
---> nothing special to note.
ArcGIS 10.7.1 Issues Addressed List - Page 5
https://downloads.esri.com/support/downloads/other_/1071-IssuesAddressedList-06212019.pdf
---> nothing special to note.
ArcGIS 10.7 Issues Addressed List - Page 11
https://downloads.esri.com/support/downloads/other_/107-IssuesAddressedList-03182019.pdf
---> First version to support azure sql
Conclusion
Use the latest arcmap/ arcgis pro to create the latest enterprise geodatabase to have less bugs.
In General...
https://enterprise.arcgis.com/en/server/latest/manage-data/windows/client-geodatabase-compatibility.htm
enterprise geodatabase version is primarily used by Esri Support to troubleshoot issues; it does not entirely reflect the functionality available to you, as a lot of geodatabase functionality is implemented in the clients that access the geodatabase and not in the geodatabase itself.
For enterprise geodatabases, the geodatabase version mostly only reflects what software version you used to create or upgrade the geodatabase.
https://desktop.arcgis.com/en/system-requirements/latest/databases-in-the-cloud.htm
And you only need make sure the azure sql cloud version is compat with the geodatabase.
In Reality
https://support.esri.com/en/technical-article/000017062
--->not too much to be aware of from deprecation notice
ArcGIS Enterprise 10.9.1 Issues Addressed List - Page 13 - Enterprise Geodatabase
https://downloads.esri.com/support/downloads/other_/1091-IssuesAddressedList_111921.pdf
--> there are some bug fixes for enterprise geodatabase on azure sql. It's fine.
ArcGIS Enterprise 10.9 Issues Addressed List - Page 12 - Enterprise Geodatabase
https://downloads.esri.com/support/downloads/other_/109-IssuesAddressedList-081021.pdf
--> some bug fixes for enterprise geodatabase upgrade from 10.7.1 to 10.8.1. It's fine.
ArcGIS 10.8.1 Issues Addressed List - Page 6
https://downloads.esri.com/support/downloads/other_/1081-IssuesAddressedList-072420.pdf
--> bug BUG-000126821 - Upgrading an SDE schema geodatabase to version 10.6 or later as the SDE user fails with a -37 error if the geodatabase contains feature classes with non-versioned archiving. will be an issue if someone tries to upgrade to 10.8 from >= 10.6
ArcGIS 10.8 Issues Addressed List - Page 5
https://downloads.esri.com/support/downloads/other_/108-IssuesAddressedList-02132020.pdf
---> nothing special to note.
ArcGIS 10.7.1 Issues Addressed List - Page 5
https://downloads.esri.com/support/downloads/other_/1071-IssuesAddressedList-06212019.pdf
---> nothing special to note.
ArcGIS 10.7 Issues Addressed List - Page 11
https://downloads.esri.com/support/downloads/other_/107-IssuesAddressedList-03182019.pdf
---> First version to support azure sql
Conclusion
Use the latest arcmap/ arcgis pro to create the latest enterprise geodatabase to have less bugs.