If this is a VM, video playback stutters do not surprise me one bit. There’s many layers between the video and the image you see on screen here and they’re not optimised for viewing fidelity. This is likely not due to Linux but because you’re running this inside a with an emulated GPU. GUIs in VMs usually suck.
Optional codecs won’t help for Youtube since they serve royalty-free codecs such as VP9 or AV1 most of the time rather than patent-encoumbered codecs such as H.264 and free codecs are always installed.
That would also not fix stutters, only videos not playing back at all (because there’d be no decoder that could).
If this is a VM, installing the Nvidia driver also won’t do anything because the machine has no access to your host’s GPU. Not that the nvidia driver would change anything about videos since no sane browser supports their proprietary crap driver, so it’s software decoding either way.
You should try this on real hardware. You technically don’t even need to install as most GUI distros have a graphical installer with Firefox etc. pre-installed that you can use to test this.
If you have an Nvidia GPU, I’d recommend you to try !pop_os.