Another thing that may help your framerates is to uninstall the NVidia 3d vision and geoforce experience programs (you should reboot after doing this). These seems to drag down all Windows mixed reality performance (esp. the 3d vision one) right now for all wmr headsets, but esp. the Samsung. The 3d vision program/feature is only needed if you are using 3d shutter glasses (like some 3d TV's use). I doubt that many actually use these anymore, esp. since the VR era.
When I update my NVidia drivers I always select the custom install and un-check 3d vision drivers and geoforce experience. Neither of these add any value to wmr right now imho.
Also, you really need to try new settings one at a time to see the effect. For example, I actually found that I got better FPS using SS = 0.9 than I did on 0.8 or below, or 1.0 and above. Not sure why but it might have something to do with the way SteamVR scales to your headset resolution. Since your Samsung headset is slightly higher resolution you may find 0.8 works best, but who knows. I also found that the last 2 bottom items on the RF8 quality pane worked best if they were both set to highest. RF VR quality set to high also seems to work best for me.
Lastly, there are so many NVidia control panel 3d settings that you can select that it can get a bit confusing at times. I have played with all of them and never found a best case for RF8-VR. I've actually found the best results by simply going to the NVidia's control panel and using the top option to adjust settings with preference. then select the 3rd one down and move the slider to the middle = Preferred emphasis = Balanced. I'm not sure why but this has improved all my wmr vr apps, including RF8. Surprisingly this has not had any significant effect on any of my non-vr games/apps performance/fps (like even RF8 in non-vr mode). If you do this you should do a reboot. Worth a try, and nothing to lose imho.
Edit; the Very last thing I would add is to play with your wmr headset settings (auto-low-med-high-highest beta). In my case I have found that selecting high helps improve my wmr and Steam apps. If you change these settings you must exit out of wmr and restat wmr btw.