Happy birthday BeamNG!

How's silly that lower settings look worse than higher settings?
Generally talking, that's how it works in PC Games. If you have the hardware to use higher settings (and do use higher settings), you'll get nicer graphics. Else you get potato graphics
Unless you are playing on an Integrated Card or something else that is below the minimum requirements, turning that shader setting to low (at least, would enable normal maps) should have near zero impact on performance.