As long as you can get to the boot screen and pick which partition to boot from then this is ok (although since I’ve also added a PC version (unflashed) of an Nvidia 750 Ti, whenever I want to switch OSes, I have to switch my monitor cable between the stock Mac ATI card, and then switch it back to my 750 Ti after I’ve picked which OS I want to boot). to select to boot back to MacOS from Windows. The main feature I’m particularly missing is the Bootcamp systray app in Windows to allow you to pick your boot drive, i.e. The Bootcamp driver download from Apple though is no longer supported on a 2008: Windows 10 runs surprisingly well on my (new) Mac Pro 2008.
