Hi, you don't have to have ProctorU on your phone. The proctor will ask you to use your Macbook camer to check your room and your desk area, then he or she will ask you to use a mirror or the selfie mode on your phone to check your laptop.
i have not used that before, but i did take my flex in "night shift mode."
i think it'll be okay, but i would just send a quick email to confirm with lsac.