With a Noise Reduction FX, I would always add this last in the FX chain because some other FX (e.g. color grading) will probably alter the grain that the NR FX has to deal with.
When using Vegas Levels, I will always put this FX first in the chain because any additional color grading (e.g. gamma, saturation) is then based on a basic color balanced image. I use NewBlueFX Colorfast 2 a lot. There is a noticeble difference in the video event's image if I swap the Levels FX before and after the Colorfast 2 FX. IMO, Levels sets the basis of the image, and other FX finetune it.
Often, the order of the FX in the chain doesn't matter noticeably, but the best way to check it out is to swap (drag/move L or R) the FX to see if it makes any difference for your set of circumstances.
I mean if it is better to add the effects as in the first video or as in the second. Clicking on the "FX" button as in the first video or dragging the image of the eye as in the second.
Sorry, but I have no clue as to what you are trying to do here.
I had a question with Dexcon's first comment. I use 4 corrections in my renderings, color corrector (secondary), brightness and contrast, sharpen, and neat video. What is the best order if I use these 4?
@riu ... Personally, I would use brightness and contrast first and color corrector (secondary) next because CC(S) will then take into account any adjustments made with brightness and contrast. IMO, if CC(S) is used first, the grading achieved would then possibly be changed by then altering brightness and contrast, possibly meaning having to go back and make some corrections to CC(S). Keep in mind that CC(S) is localised depending on your masking choices, whereas brightness and contrast is global for the whole video event.
Sharpen and NR (e.g. Neat) should be used last IMO as they then have the corrected image to deal with. I should add here that I do not use Neat but instead use BCC's Noise Reduction plugin which includes sharpening as one of the adjustments if that adjustment is needed. For me, I always place the NR plugin last in the FX chain.
Others on the forum who use Neat may have specific advice in relation to using Neat.
EDIT: If you are dealing a lot with dark images and are crushing the blacks via brightness and contrast, it's better to do that first as you might well reduce the need for, or the aggressiveness of, noise reduction. Also re blacks, also consider using the gamma control in Color Corrector in combination with brightness and contrast. I find that a nice balance can be achieved in balancing gamma/contrast (though to be fair I am using NewBlueFX ColorFast 2) to get decent blacks while retaining detail within those darker images.