Please use browser inspector options or plugins to find them like we would do it with any other CSS customizations as well.
Sorry, I am not following that.
In general, the SuperGrid block is just a different styling for “Pages record feeds”. There is nothing special about it and it shouldn’t depend on any other blocks. You should be able to create a regular feed block – see it working – and then add the SuperGrid theme later to it. That should change the appearance, but show exactly the same entries as before.