Navigation Button: On S8 if you prefer back button on right & recent app on left, so you can swap them as default order.
Play Music at a time on two devices: In S8 there is a feature named Dual Audio you have to just go on Bluetooth Setting press the menu button and there you will Dual Audio just press it will connect your two device like headphone and Bluetooth music system.
Customise Color: In S8 you can custom your navigation Bar Color.
Sensitivity of Home Button: In S8 you can set your home button Sensitivity (increase or decrease).
Doctor Appointment: In S8 there is a option Amwell if you open Samsung Health option there is expert if you subscribe you can contact doctor at any time.
App Shortcuts: In S8 if you long press on any app shortcut there you will find few option (just like 3d touch in iphone).
How to Zoom in and Zoom out: In S8 onscreen shutter button up or down to zoom in and out.
Shrink your Screen: In S8 there is a one handed option if you will enable it screen gone shrink.
Performance Mode: In S8 if you remember in previous model there is only two option now there one option more added Optimised(recommended)