By default, feedback and grades are available to students as soon as they are entered. If you want to hide feedback and grades on an assignment, toggle off the Show feedback & scores option at the top right. With this option disabled, students can still submit and critique videos, but they will not see any feedback (comments, markers, etc.) or grades (including rubrics).
With the Show feedback & scores option on, students will be able to see feedback (according to the assignment privacy settings) and grades (on their submission only).
If you are using GoReact in an LMS (Canvas, Blackboard, etc.), turning off Show feedback & scores will also prevent grades from being passed to the LMS gradebook. Once Show feedback & scores is on, all grades will be pushed to your LMS gradebook.