Yah, ReShade is a must have in DCS. It used to be that Sweet FX/Reshade had no effect on FPS. Since the last few updates, however, it now costs some frames. 5 to 15% depending on your settings.
Still well worth it.
BTW Snacko, Reshade is supposed to be run in "Performance" mode always. Only put it in "Configuration" mode when changing settings.