If you're using Class Code - Shared Device Sign In
and you turn "Students can see each other's work" OFF, students will not be able to see any journal content at all- including their own. They can only add items. This is because we do not know which student is signed in, and therefore do not know whose journal to display.
In Class Code - 1:1 Device Sign in and Email/Google Account Sign In
if "Students can see each other's work" is OFF, students will be able to see their own journal, but not other students' journals in the class.