If your device is rooted, you can uninstall the stock camera and make google cam as default.
No need to root, you can remove it using ADB commands
Android 10 has removed system partition in all devices and has chosen for super partition.
So there is a super partition
Are people stupid here? You literally cannot port Oxygen Os, it's not open source neither it can be ported for all devices. Many custom roms are better than oxygen os.
Is 256gb variant special edition ? Is the firmware different from others variants ?
Nope, the only difference SE gets is the names of Fans on its packaging