@Man - Depends on the delivery server type you create, if the delivery server type is a web api one, then you don't need the bounce server field therefore it is not shown but if you create a smtp server then you def. will get that field.
If I use amazon ses and also created a bounce server, because amazon prefers that we use server for bounce handling... does that mean my amazon ses send server won't use my bounce server that i created?
Mailwizz supports amazon ses as smtp and also as web api. If you use smtp you'll be able to select the bounce server. If you use web api you can't select the bounce server because there is no need for this.