The Sales and Service Hubs in Dynamics 365 v9 are basically applications.
You can create and customize you own application and provide the users that functionality that they need from the applications, which use the Unified Interface in Dynamics 365.
For example you can set which forms and which views will be included in each entity on the Application that will be rendered via the Unified Interface.
Advanced Find is currently not available in Unified Interface, and I am not sure what the plans are for that.
The editable grid should be available in the Unified Interface. It is possible that for the form you were viewing it was not included in the application
Most of the Administrative features that are available in D365 are not available in the Unified Interface either.
I think it is a matter of deciding what features you are looking for and whether or not the look and feel of the Dynamics 365 System or the Application is what is right for your users.
Hope this helps.