The self adhesive stuff is excellent, its also nice and easy to work with, I have used it in my room and have also covered my front two atmos speakers and half of my surround speakers to stop reflections catching your eye, I'd certainly recommend anyone who is serous about a complete bat cave, to at least have a roll handy.
Another advantage of the MVEL22 though is that its also acoustically transparent.
I have curtains that pull over my sidewalls, I've just installed front wide speakers, the curtains pull over these so they can't be seen.