We are also facing same kind of problems. Is it possible to avoid listing our app in this login items? Or can we get some notification in case if user switched this button off so that we can ask user to be sure before doing this and its consequences?

Yes, I verified on macOS 11 beta 9 (mac mini 2014). Me too found same issue with images if we try to present in NSImageView. Looks like pixels are getting overlap as per my observation. But same look all good on macOS 10.15.

Reported Bug Id : 8736010