The open kernel packages are open source, and can be found here: GitHub - NVIDIA/open-gpu-kernel-modules: NVIDIA Linux open GPU kernel module source for which the current README is here: Chapter 45. Open Linux Kernel Modules
For me, the main difference between this and the proprietary is this listed "known issue":
- Run Time D3 (RTD3) is only supported on Ampere and above GPUs.
I'm still getting my head around what this means exactly for me, but essentially it's to do with being able to enter the lowest power states (see Chapter 22. PCI-Express Runtime D3 (RTD3) Power Management).
The proprietary driver is being phased out - thankfully.
A metapackage is basically a package that doesn't contain any real material itself, it just lists packages that it depends upon. These includes packages like ubuntu-desktop.
I think most of the NVIDIA-supplied drivers are metapackages now.