Crosire is absolutly right and since you seem already to know about how to use LUT.
If you are not familiar with photoshop I suggest the following.
Run the preview feature in the mediator and apply all color correction/contrast effects that you need plus one of the curve passes.
Now press L+prtscr to generate the LUT within a ReShade screenshot.
Disable all effects and only apply the just created LUT to the preview feature.
Now you have the choice to apply another curve pass and be done or even create another LUT to get rid of all color correction/contrast performance impact
EDIT: sorry, read your post too late, good you solved it the way its most efficient