When designing courses, experiencing the course as a student is mission critical. While there is a Student Preview, it is not 100% accurate--and is a bit clunky. While the student preview is pretty good at helping you understand how the course looks, it is not entirely reliable (for instance, submitting work in the student preview can trigger errors and the User Lists tool is confusing to understand).
There is a also built-in productivity hit when using the Student Preview - once engaged, Brightspace will take you back to the top level of the course (which is very frustrating if you are several levels in). Happily, there is a workaround!
I recommend opening a sacrificial tab.
Open a second tab in your browser - this is your sacrificial tab. It will only be used to toggle between student view and instructor view. Next, go into any of your courses in Brightspace. Flip the perspective to the student view. Then, navigate to your primary Brightspace tab and hit refresh. You'll find that when the page refreshes, you will be in the same spot you just were - but with a student view!
When you are ready to get back to the instructor's view, go to your sacrificial tab and change the perspective back to the instructor. When you go back to your primary tab just refresh and you'll be on your way!