GL3.3 is not fully supported yet, so those overrides are necessary for OBS for the time being; that’s working as intended. The version the driver advertises (GL3.1, GLES3.1) is what is fully supported. Software like OBS can work with the overrides, but that doesn’t mean those versions are fully supported.
openh264 should actually be installed by default on F38/F39, but yeah, it looks like there are no rawhide packages.
Can the active screen area be made to stretch up beyond the position of the webcam?
Yes but no desktop environment today has proper notch support (e.g. to avoid fullscreening apps under the notch), which is why this isn’t enabled by default and never will be (once a standard for this and DE support materializes, it will be automatically opted-in by compositors which support it, but the default will always be no notch). Use the apple_dcp.show_notch module param.