You can provision a VHDX on your pre-existing NTFS volume (IIRC VHDX overhead is <=1% for Hyper-V, not sure if that's still the case and/or applies to DevDrive). But yes, I would say an additional drive is ideal. I did just that to put games on DevDrive.

https://devblogs.microsoft.com/visualstudio/devdrive/

https://learn.microsoft.com/en-us/windows/dev-drive/#set-up-...