A few questions regarding the new ST app vs ST classic

To add to what Nathan said, see the image on the first post which explains how ST works, you’ll see that the new/classic apps are just different user interfaces to access your account on the platform. So the core it the same, how they’re displayed are different and then each app has access to certain features on the platform that the other app doesn’t (e.g. new app provides Automations, the classic app provides custom UI’s etc).