Blurry FaceTime: this probably isn't helpful, but prior to Catalina I used a legacy Firewire iSight camera (the one that was supported above the display by a flexible gooseneck). Prior to Mojave, it worked great. However, beginning with Mojave, the video was low-resolution in FaceTime but was clear in other apps (this was prior to the Zoom days). I never figured out what the issue was, and my problem went away when I learned that Catalina dropped support for the iSight microphone, and I relegated the iSight to the parts bin.