When you use a scene it works the same like only with 2.5 and direct inputs. But if you loose internet connection it only works locally with Shelly App.
If you use local actions you can only set one action per button. Go up/down or to specific percentage.
You can't define to go down as long as pressing the button for example.
But you could say go up/down when pressing button and stop when pressing long/2x times or so.
Local actions only need local WiFi and no internet connection.