Im looking for a mixer that allow me to balance 2 input for 2 distinct outputs. What are these mixers called?
You may want to look at "Zone Mixers" or "Matrix Mixers".
An example would be here (this is just an example, I have no affiliation with website nor product)
One thing to keep in mind with such equipment is that inputs, as well as outputs, are usually single (mono) channels, and therefore you need to use 2 inputs, and 2 outputs if you desire stereo.