There are a few key differences. It doesn't appear that you have limit transfers to your contacts, but you can specify "Preferred Visibility" so that you can see when you're not using Fast Share. The sample recipients in the Fast Share screen suggest this may be available on Chromebooks, iOS devices and even Wear OS smart watches, although we would not count on all of them being available when the feature goes public. In iOS version would require a special app.
It's not certain when Fast Share will launch, although it's a Google Play services feature and probably wouldn't have Android Q. Google might not wait long, though. The company has warned that it's deprecating NFC-based Android Beam transfers in Q. As such, Fast Share could be the only way to quickly send files to local users without apps to apps (like Files by Google) garden.