Separated aim/look has to be supported by games themselves (or with mods), that’s not something that can be implemented retroactively on the DirectX/OpenGL level unfortunately.
One such game is Arma III, which is able to do this natively. You will also need an external tool (OpenTrack) to use the separated aim/look with Arma.
A more popular game that allows this with a mod and vorpX is GTA V. The mod can be found here http://grandtheftvr.com. It has alpha Vive support. Oculus only works until runtime 0.8 (DK2) though as far as I’m aware.
In regard to image quality try higher game resolutios. The default suggestion of 1280×1024 is a general compromise between performance and quality. For better quality try 1600×1200 or 1920×1440. The latter provides the same image quality as native apps have, but might be too slow for newer games. So always keep an eye on performance when trying higher resolutions. You can check the current frame rate with ALT+F. 45+ game fps are required for a comfortable experience. In the long run a reasonable framerate is the most important thing.