I am working on multiple AEM implementations. Given most of the implementations would have huge number of assets, we want to have a centralized/Enterprise DAM implementation.
1. Please share your insights around AEM solution based on the centralized/Enterprise DAM. Please share the Logical/Physical architecture if available
2. How component authoring was enabled to select assets from centralized DAM? Connectors to integrate the content finder with external DAM?
3. Any non AEM based systems, would they still have to refer the assets through URL's?
3. Any documentation, blogs available would be of great help
Check out AEM Brand Portal which seems like it matches your needs:
Overview of AEM Assets Brand Portal
Thanks Shunnar. Specific to AEM integration, are you suggesting that we setup AEM integration as Configure AEM Assets integration with Brand Portal ?
We also have Adobe Dynamic Media Integration for AEM image assets. Would Brand Portal would be integrated with Dynamic Media as well?
-> Would Brand Portal would be integrated with Dynamic Media as well?
yes, see 
Also, see other integration options available with the AEM.
 Overview of AEM Assets Brand Portal
Asset link sharing
 Configuring AEM Assets integration with Marketing Cloud and Creative Cloud