Why is deltaTime different in BP and C++?

I’m trying to make a game that works correctly on all computers at varying fps.

I’m new to using variable DeltaTime.

Before I hardcoded my games for 60 fps and enabled vSync& then it would just work deterministic.

Now I’m learning Unreal and don’t know the correct way to make games with it.

I want to make something like this
https://www.youtube.com/watch?v=ny7mLmslkCg

But I don’t know how to do that flawlessly.

Do I have animations drive the gameplay?

Or do I have to preprocess everything into physics calculations & events and sync with that?