I'm running an AMD RX 480 graphics card, and the driver for it on Windows 8.1 has not had an update since Mid 2017. However, I have noticed that regarding Windows 10, This card still receives frequent updates. Would it be inadvisable to download the driver for Windows 10 while not actually using that OS just to have a more up to date one for my card?
No....it wouldn't install/perform correctly. Windows8.1 will receive no more updates.