1. In order to monitor all hosts with a single Veeam ONE server, you need to deploy a dedicated SQL Server and make sure you size your Veeam ONE server accordingly. I would recommend to start from 8 vCPUs and 24 GBs of RAM, also fast disk drives for both the SQL Server and Veeam ONE servers is highly recommended.
If you are still not in touch with one of our system engineers, then I would suggest doing that, as our SE can assist you with Veeam ONE deployment and evaluation. Can you please tell me what region you are at?
2. Our Veeam sales rep or system engineer should help with this question too. They will be able to walk you through the list of differentiators and answer all questions you might have on this topic.