Nvidia Pascal on Mac Pro 2010
If your current card is working adequately for you in what is by digital standards an ancient machine I would not change anything.
If you are bound to upgrade I would recommend you seek out an nVidia card in the 900 or 1000 series that is entirely bus powered, does not require additional power connections from the power supply.
In a hackintosh switching to nVidia initially requires the use of boot flags until the nVidia drivers are installed or the machine will not boot or go into kernel panic. I do not know if that is an issue with an older Mac Pro but I would look into it if I were you.
Nvidia's ongoing support for its hardware in OSX despite the fact the Apple has used only AMD parts for several generations has benefited the Hackintosh community more than Apple users. The types of video driver updates important for high end Window uses like gaming are irrelevant in OSX.
I hope that Nvidia support for Pascal means those parts, hopefully mated to AMD Ryzen chips, will power new Apple machines. In truth whatever OSX power users there are (who would all be better off on Windows or hackintoshes) would benefit more from a higher core count than a Windows style gaming card as the only need, given the structure of OSX metal, is the ability to drive 4k or 5k displays.
Im using rx 480 but the problem is that it's not even fully supported for MacOS so it performs as same as HD5870. Why did I pay it for...
Im thinking to get 1070 8gb for adobe programs. I don't think that Im optimized for AMD gpu since adobe is more nvidia friendly.