Hi,
yes, I mean the “RENDER SCALING” value : 50…60… try what you PC is able to handle and what is looking good for you 
What do this setting:
If you not use native screen resolution, then your image becomes often kind of blury. To avoid that, you can set that the game use your full native monitor resolution, but render the in-game sceneries with a lower resolution and let later scaling it to your native resolution. This safes a lot of graphics-power and the result is very often not bad.
One note: if you stay at 50 , you can try whether your monitor do this job better. Because you have a full 4K monitor , the resoultion of Full-HD ( 1920x1080 ) can very good scaled. Then, in theory, it should be same that you set RENDER SCALINNG:100 , but SCREEN RESOLUTION to 1920x1080. But, it is theory,… nobody know how these code is implemented
Vsync setting is for syncing your PC with your Monitor… The Graphicscards waits, if the monitor can not show the images faster, result: no Tearing and not feel of stutters.
I assume you have a 60fps 4K monitor. Then let the value at 60, because there is currently a Vsync Bug.
Related to your GXT1660 it might be good choice to lower some settings.
Here is a HowTo Thread which explain a bit the settings ( follow it for discussions thread ).
But be aware:
- change things step by step
- always change only one setting and try it
- search for GPU relevant settings
- I recommend the reversed way:
– that you start with the MEDIUM Pre-Set and slowly increase some settings to High