For playtesting, try to change all of the values, saving and loading them. To make sure that the scripts work, just place all three scripts onto the same GameObject in every scene you have. For the quality settings, you will need to modify the native Quality settings in Unity. To do this, click on Edit, hover over Project Settings, and click on Quality. An Inspector window should appear on the right-hand side. Here, you will want to delete the default settings until there are three left, which will be Low, Medium, and High. It should look like this now: