The only credentials required for the AppInsight for SQL are "sa" or equivalent SQL credentials. You can also use Windows credentials provided your SQL server is configured to use Windows Authentication. 95% of all information collected by AppInsight is collected directly via SQL queries, so it can be used with both SNMP and WMI monitored nodes in Orion.
However, if the Node is managed in Orion via WMI you get some extra goodies, like the Windows Event Log Monitor resource that monitors the Windows Event Log for Warning/Critical events related to that specific SQL instance. You also get the Database Disk I/O, and Transaction Log Disk I/O resources on the Database Details view. These two resources are also dependent upon you monitoring the volumes where these files are located on the SQL Servers file system. This is also integrally linked into the Database Size by File and Transaction Log Size by File resources to properly calculate available space for databases configured to use auto-grow.
If there's some information you're not seeing please let us know what that is specifically. It may be that the SQL user account you're using doesn't have adequate permissions. As stated above, try using an account with "sa" or or equivalent SQL permissions to the SQL Server instance. We will be documenting the specific permissions required to use AppInsight with a "least privilege" account that should be available at the time of official release. This is being tracked internally under FB246926.
As for the performance issue you're seeing, this is beta code that has not yet been fully optimized. However, PLEASE continue to tell use when and where you're seeing unusually long delays with pages loading. I've logged the one you reported above and we are now tracking this internally under FB247785.
