I forget to blog that the breeze icon set get full gnome support. You can test it with the upcomming plasma 5.8 release. Don`t forget to test the beta and fill bug report.
95% of the awesome gnome icon set adwaita are available in breeze. The missing ones I didn`t know where they were used or they are needed only in a gnome session.
Plasma open for 3rd party apps to support the best experience for the user.