For example, in properties> Output, if I have choosen 8 bits, does this affect the baked color? So, do I have to select 16 bit and rebake it or is enough export it to 16 bit?
Blender works in OpenEXR under the hood, so when you indicate a full float image in the Image Editor, and then bake, if you choose 16 bit then you will get the 16 bit version on save. If you choose lower quality, that is what blender will write to disk.