I can confirm on my GeForce 750 Ti (2 GB card) on Windows, everything was ok to run any workloads I wanted and it offloaded things to system memory seamlessly. It did this since 2014 when I put together this system.
On the same system but running Arch Linux (any Wayland DE) with the latest 580 drivers, I could barely open a few browsers and terminals before going out of GPU memory and things would crash or stop working normally. I included way more details in one of the threads you linked at Non-existent shared VRAM on NVIDIA Linux drivers .
I ended up spending almost 2 full weeks troubleshooting as much as I could, wrote an 8,500 word blog post, made videos, opened issues on GitHub which got a reply from NVIDIA, but no resolution.
All in all, since then I still use the same system but I switched to an AMD GPU (RX 480) and this problem went away entirely. I’m only posting this piece of information to confirm it very strongly appears to be a problem with NVIDIA drivers but not AMD.