Window Manipulator provides three main options to customize the screen density on your phone: Density, Screen Size, and Overscan Area. Each option has a Reset button beneath it, so if you get too far away from that stock look, you can always go back.
Rather than having a specific DPI value for each different device, Android groups displays with similar DPI values together. As such, there are currently 7 different DPIs that Android supports natively:
While DPI values that fall in between these numbers will still function properly for the most part, only these values will ensure that no minor cropping, stretching, or overlapping of icons will occur.
With that in mind, tap the Set Density option and enter your desired DPI value. As a general rule, the smaller DPI value you enter here, the smaller your icons and visual assets will appear. So with a stock DPI value of 480 on the Galaxy S5, enter a lower number for smaller icons or a higher number for larger icons.