On another point, I finally found a way to tweak my render settings to have a result noise free, or at least a lot better as you can compare with both pictures... but it take too god damn long 15h (and I stopped it at 75%), so I have to tweak some more and find a compromise.
But in the end, happy to have finally been able to solve it in part, I knew it was a problem with my lightings during scenes with few light (and sadely the intro as lot of scenes with few light), now I have to find a good compromise between time and quality, because as much as I want to give quality if I stay at 10h+ by render, I will give update only once a year. I want good render, but I also want a good number of renders in my updates.