Seconded on the first point, AMDGPU is indeed far better than really anything else on Linux. As much as I try to run it on my main machine, I end up taking up gaming again or something and end up chafing and reinstalling Windows before too long much as I hate Microsoft as a company.AMD's drivers are better on the Linux side and yes, they've always kinda sucked for Windows.
On the other hand, my life-long experience with nVidia has involved under-specified fans that would kill cards. To this day I still don't trust anything with an nVidia GPU that's not on a dual-slot cooling solution. There was a point in time when Dell was sticking low-spec video cards in everything and every time a Dimension something-or-other crapped out it the fix would be to swap in some other cheap POS GPU.
As for the second, I have a PCI GeForce4 MX4000 that originally came with a TINY heatsink and no fan at all. I modified the heatsink from a dead AGP card -- literally filed out a little spot for one of the quartz crystals to poke through so it'd sit flush -- and it runs far cooler. I keep it around on the off-chance I end up with a Socket 370 or 478 board that's PCI-only, as their integrated graphics reek.
Thankfully I don't have to worry about cost-cutting designs with my 1070, it's the superclocked version from EVGA. I'll be cleaning it and repasting it as a matter of course, and making sure the fans are in decent shape.