"Create an msdos startup disk"
What does this feature do? It occurs when I want to format a flash drive/disk. Why is it greyed out for me? 
This feature requires a 3.5" floppy and is included for backward compatibility. It allows you to create a MS-DOS bootable 3.5" floppy disk. Typically this would be used to boot to in the event of a system failure and you needed to troubleshoot of attempt to retrieve data, but there are now so many other more practical options that it is rarely used. Not to mention there are basically zero modern systems that include 3.5" floppies any longer.