You may grow to understand why pCARS is a love/hate proposition for many of us 8)
For Assetto, make sure the in game screen resolution matches your monitor resolution. A quarter of the screen reads like its set to 600x800. No auto detect in AC from memory.
I think the problem is I've got a 4K TV mounted to my cockpit, but I've got AC set to output 1080p (for performance reasons). For some reason the TV isn't upscaling the image to fill the screen.
 
	 
				
 
 
		 
	

 I've just tried to get the same deal (as a previous iRacing subscriber) and I'm greeted with this:
 I've just tried to get the same deal (as a previous iRacing subscriber) and I'm greeted with this: