A feature that I miss from my Galaxy note 4 was that you can long press the numbers and it will insert some text you have saved under that number. I used this a lot in my work to text my clients with various standard messages. It's really useful. I recently tried a Galaxy S8 but it didn't have this feature (called Hotkeys). I know there is a way to replace some short text with along text (text shortcuts), but that's not nearly as easy as just long pressing a number.
I have resisted upgrading my Note 4 mainly because I would miss that feature too much. Is the feature available on the SwiftKey keyboard? I think I read somewhere that the Galaxy Note 4 keyboard was from SwiftKey.