Scriptable Objects have been around in Unity since 2012 with the release of Unity 4…wow that was a long time ago! Anyway these are pretty handy and I’m surprised by the amount of people I come across that either don’t know what they are, or how to use them.
IMGUI (Immediate Mode GUI) is Unitys legacy UI system that handles game UI pre-Unity 4.6 and editor UI. It generally consts of GUI.xyz and GUILayout.xyz calls within an OnGUI function. It could get cumbersome and very difficult to read. Especially if you have a lot of GUI controls.