Originally Posted by JustinGGX
If I set my Xbox One X on my KDL55W900A to Full it looks very washed out :/
Which device are you setting to "full"? The W905 TV in it's HDMI input settings, or the Xbox in its output settings? If you change the one, you must also change the other.
Box-output to limited and TV HDMI-input to limited, or TV-in to full and box-out to full, will both result in the same range of picture contrast. Only thing is, as far as games are concerned, with the limited variant you're loosing approx. 13% of shading accuracy. (Engine is natively rendering 255 shades, output is reduced to 220 shades, guess where the loss might be.)
Of course you can use the limited/imited combination also for games, the edge values of blacklevel/whitelevel/contrast will be correct. But for the 13% loss of shading accuracy.
But well then, it must also be noted that the Xbox boxes are a surprise-bag in themselves. For some reason Microsoft decided to make their boxes to not output a stable gamma-curve, the MS engine is always tinkering with the gamma curve in some (unpredictable) way. Which eventually might affect the decision which kind of setting might look better than the other. But that's a specific problem (potentially) with Microsoft boxes. The general answer is as simple as that: for video games, the preferred option should be RGB @ full/full. That is how RGB (gaming) is working.
I don't have a X-One just a X360, but that combo is running since day one with X360 output = full ("extended") and W905 HDMI input =full, and there surely nothing is "washed out". Black is on-spot black. (do I set W905 brightness 1 point less from 50 - nothing happens, do I set W905 brightness 1 point more than 50 - black brightens up. It won't get more correct than that.)