If you want to back up the SQL Server database in native format (fulls, differentials, and t-log backups), then you'll need the SQL Server Edition. If you did not have a SQL Server need, then you could use the Virtual Edition and perform host-level backups of the VMs. But in your case, you may be best served using, 2 licenses of Server edition (or Desktop / Server depending on what licenses you see in your Managed Backup license page) for the Print Server and Lotus Notes Database VMs, and 1 licenses of the SQL Server edition on the SQL Server VM.

If you want to discuss options in more detail with your account manager, you can reach out to them for assistance.