Do I need a Windows VPS or Dedicated Server?

No, you do not need either a Windows VPS or dedicated server.

SMP is a standard Windows application, designed to work on machines with the Windows operating system. It will work on most Windows PC's, laptops and tablets.

If you wish to leave SMP running for long periods (e.g. 7 days, 24 hours) then you "might" consider using either a VPS, or dedicated server for convenience...but even then, it is not necessary (you can leave it running on your home PC if you chose).