In scenario 1 (using MB as is), we don’t consider the entire system as a derivative work, since you’re using MB as it was meant to be used – an application to access data in a database.
In scenario 2, you’re under https://www.metabase.com/license/embedding/ which explicitly says you don’t need to worry about the AGPL so long as you leave our logo in there. If you want to remove it, the premium license you linked to applies.
Our posture is a little different if you’re trying to embed our entire interface in your application, modify the actual program itself, etc. The situations you describe are standard vanilla modes of operation that we definitely don’t want to encumber in any way.
Does that all make sense?