1. You mean a full page youtune replacement UI? 2. There currently is a CPU hungry bug only for the moment while you are changing our settings and only in Firefox.
EDIT: Blank page? why and how? Did you check the browser console before? If it is related to one of our features the will you use our github bug report form please? (I shouldn't type this 1000s of times and Firefox feedback is not meant to be bad for bug reports. It will be remove then.)