For everyone who finds this - I solved the issue with Overwatch error / No compatible graphics hardware was found 0xE0070150 - and also Bethesda games (like Skyrim or Fallout 4) not detecting the resolution and unable to fullscreen!!!
Please mods, read this so you can make sure it reaches other people in need -
The fix is simple -
Go to Radeon drivers and ENABLE GPU SCALING!!!
Now I dont know why this setting is OFF by default in the new driver versions
For reference, my system is Windows 7 and I have RX480