1) most probably if you take into account other factors (social economics ones), the nationality it's not a major one
2) as you said, the wealth created by migrants can be a net positive effect
3) many immigrants (85%) come from EU
4) almost none "ethnic ghettos" in CH
5) agree it's different. CH has about a 1/3 of its population that are migrants and they are generally welcomed and integrated (the regions that got most migrants rejected the initiative).
Beside, there isn't a unified "swiss culture". If you simply look at the languages, they are 3 different ones.