OK, DurgeDriven's basic advice above matches mine. This setting has now allowed me to run with no AA whatsoever on a number of titles and they look stunning.
Unfortunately, since the beginning of rF1, neither rf1 nor rF2 look truly good unless SGSS is used. Even 8x supersampling still results in shimmering and ugly looking effects all over the place. DSR does not change that at all. Apply SGSS and suddenly the digitized pixelated world that you are used to suffering through quietens down into a solid, pleasant result--that if matched with realistic graphics like feels3 tracks, proper HDR settings and rF2's nice lighting system--can blow you away in terms of immersion.
The problem is that DSR is a general setting that even affects desktop. You cannot turn it on and off by individual title as far as I know. So you will likely want it on for many other titles, even if it has no effect on rF2.
However, if you haven't been using SGSS or regular super-sampling, this MIGHT provide a similar quality improvement at approximately the same FPS hit, but either the performance or quality may be slightly more to your liking, so I would try it out if it's an option.
But, if you have never been able to use super-sampling due to performance issues, you can hit ignore. This isn't "free" higher quality graphics.
And lastly, because I know how confusing all this stuff gets, SGSS (available only through special programs you have to install like NVIDIA Inspector) is also a performance hit over regular super-sampling. It looks a hell of a lot better, but it sadly isn't free, either.