Hello Stefan,
I found a technet stating that we should run SharePoint 2016 content databases on SQL Server 2016 in compatiblity mode 110.
Symptom
When you use SharePoint Server 2016 together with Microsoft SQL Server version 2016 or 2017, you may notice decreased query performance or increased CPU usage on the database server.
Workaround
SharePoint Server 2016 content databases that are deployed on SQL Server versions 2016 and 2017 are tested and validated to work best with compatibility level 110.
Can you please confirm this?
Thanks,
Pablo