How to sync two folders connected to the same Mac

Hello, I hope someone can help me with this - I'm sure I'm not the only one.

I manage over 20TB of archived media and project data, and I'm in the process of moving from Windows to Apple computers. On my old Windows computer, I have for example, a 2TB internal drive that I back up with a 2TB external drive (I have about a dozen of these 2TB external drives). As I work on throughout a typical day, files residing in various folders on the drive get updated. To keep my desktop drive backed up, I connect the external drive, and use a Windows-based utility (an app called Commander) that compares all the files on both drives, detects the files that have been modified, and replaces just those files on the external drive. Takes very little time, and you can imagine how long it would take if I had to copy the entire contents of a 2TB drive each time I do a backup. I need to have a backup copy on a drive that I can easily access from multiple Mac and Windows computers. So I don't think Time Machine helps in this environment. I'm hoping there is a similar utility either built in to the OS (I have Mac OS Sierra running on a 2012 Mac Pro) or perhaps one from the App store. This is something I need to resolve before I can make the Mac Pro my main desktop computer.

All suggestions welcome,

Thanks in advance!