What Thomas said, but also Rapid Setup gives you some pre-built workflows, rules, etc. that you can use instead of building your own J/M/L. Rapid Setup includes ‘flexible’ J/M/L, that gives you a fixed set of options to choose from when onboarding new applications. Via attributes on each application definition, you can then specify what should happen for this app during J/M/L (based on a fixed set of options that Rapid Setup has).
Meaning you don’t need to make any new logic when onboarding new apps, you just set the attributes in the app definition (also accessible via the UI as a wizard)