They have specifically told about this app that it would be compatible only with the Samsung Galaxy smartphones or later versions which are running Android 7.0 Nougat and the app has to be be downloaded only from Galaxy Apps store.
So it is clearly for those who are using this model, and unless the app picks up the craze, it is going to be used only by Samsung Galaxy users.
As I am not the one who could use it currently, I am unable to give you a first hand user feedback.
Secure Folder app is based on the in house Knox technology from Samsung. However, you will need to be running on Android Nougat to be able to use the application. Currently available on Galaxy S7 and the A series ( the feature was initially launched with the ill fated Galaxy Note 7), you can - for now be sure about its availabilty on your device - if your carrier has rolled out the update for your device.
Live....and Let Live!