Yes, the more to the right the slider bar is pushed, the nicer looking your circular edges will look BUT it will take longer to rebuild faces and longer, because you're in the red to open.
Keep it about 4 lines from the left...
It remains equally as geometrically precise either way, but it is the appearance that is altered in the display of curves, arcs, and circles.
If you are not experiencing slowness, try a linear pattern of these to push the limits of your system. If that's not enough to challenge performance, try a linear pattern upon that linear pattern. Then zoom in and out.
It does not slow much when working with simple parts, or few parts. You'll experience more slowness with additional complexity.
Edit: to add to what Steve Calvert mentioned, you can find rebuild times for each feature in Performance Evaluation tool included in the Evaluate tab. Even if imperceptible, times are displayed in hundredths of seconds.
I just experimented with document units precision. Even if Time unit precision is pushed to more (or less) than hundredths, Performance Evaluation still reports performance in hundredths of seconds. Hmm.
Precision does not change with these options only the graphical representation. When you zoom in on the edge of a circle you will notice it become jagged the higher this bar the more you zoom it will still stay a relatively smooth curve. The better your computer the less you will see an impact if you increase this bar. Similarly the less curves and complicated your parts and assemblies are the less of an impact this bar has on performance.
Since I work with models in the thousands of parts and lots of edge fillets I keep both of these bars set at about 10%. I also have my Optimize edge length turned off as that can have a similar impact.
I hope that helps in your understanding.
High means precision resolution of the model will become high. Slow means function of SWX will become slow.
I wish to know whether my understanding is correct. Because I do not realize any slower function of SWX.
It has to deal with the looks, not the actual precision of the dimensions. Lower both of them to ~80%