It is not possible to say how much H2S will come out. You probably would have to confirm that with a experiment.
THe only thing that can be said is that carbon dioxide comes out much more easily than the more soluble hydrogen sulfide.
You need to have the water analysis (H2S included) and flow before making any type of conclusion on the best treatment approach. The most common technique is to use aeration or degasification, and or chlorination.