When you update to windows 10, make a CLEAN REINSTALL.
On my mac pro 2010 i initially had severe problems with win 10. After a few days the windows file system always got corrupted so that it could not be repaired in any way. I always first installed win 7, installed bootcamp support drivers, then made the update to win 10.
Then after several tries i made a new and clean reinstall of win 7, NO BOOTCAMP SUPPORT drivers, then upgraded to win 10. And again NO bootcamp support drivers. For every system component i found a driver at the manufacturers web site. And after this win 10 works fast, stable, rock solid. There is no unknown device in the hardware manager.
And my 980ti works perfect too. Only display port cables longer than 2 meters will give me a screen blackout twice a week. Using cables with a maximum of 2 meter work perfect, no blackouts.
The screen artifacts you have ... your card must be defective. Or you dont have both power cables installed. The 980ti is power hungry, very very hungry.
The r9 280 drivers, did you get them here ... http://support.amd.com/en-us/kb-articles/Pages/AMD-Radeon-200-Series-Drivers.asp x
greetings from germany
Chris