From my limited research and understanding, Nvidia makes Linux drivers, but they’re closed source. These work fine. They open sourced some stuff but not enough to really change much yet.
There are also FOSS drivers, but the performance for those vary.
Is this correct? Should I stick to proprietary drivers if I want consistent performance?
damn.
Well if nothing important is on that computer, I would suggest a more conventional installation.* For instance, if you choose Mint I'd pick the option with Cinnamon, which shouldn't be that heavy even on an old laptop and would have the best support for that distro. I mean, I just run regular Gnome (in Fedora Linux) which basically has the reputation for being the heaviest desktop environment on my 12 year old Thinkpad X201 and it performs just fine. And certainly without any issues like the lock screen not working correctly when I close the lid.
*I'm implying a reinstall but you might be able to get away with just installing the Cinnamon packages and switching your display manager/environment to it.