Do we even need to care about the actual surface pixel format?
We need to provide an EGLConfig when creating a surface, otherwise EGL wouldn't know which format to use when creating the underlying surface buffers.
Same question for the contexts, can we leverage EGL_KHR_no_config_context to make things simpler?
Yes, this is possible. Again, I am not able to find any direct information about the NVIDIA or AMD proprietary extensions, but I am seeing references to it for such drivers starting around 2019, so I guess we can give it a go and see if it breaks any setups.