There are a few key differences. It doesn’t appear that you can limit transfers to your contacts, but you can specify “Preferred Visibility” so that favorites see you even when you’re not using Fast Share. The sample recipients in the Fast Share screen suggest this might be available on Chromebooks, iOS devices and even Wear OS smartwatches, although we wouldn’t count on all of those being available whenever the feature goes public. An 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 likely wouldn’t require 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 resorting to apps (like Files by Google) that your friends won’t necessarily have.