I recently filed a support request -- and this resulted in learning that there is no permissions setting to restrict edit access on quizzes next without removing the ability to grade for instructors.
We don't want all "graders" (e.g. TAs and new instructors) to be able to edit the check-in questions scattered throughout the modules.
UPDATE 5/30/2019: This may be related to it being treated as an LTI and therefore permissions are not aligned with the tool? Looking at the road map, it's supposed to be the main quiz tool in 2020, so I really hope it will be able follow the standard role/permissions that control rights around all other assignments and content in canvas.