No idea what chicken schnitzel tastes like - I am a veggie! It started by not eating veal from age five onwards.....
The Bratwurst sandwich is a form of the Chicago hotdog, I think, which is on a soft bun with sauerkraut - someone can correct me if I am incorrect about it being a Chicago style item ie that they eat their hot dogs with sauerkraut. The soft bun is not something you would see in Germany either.
And yes, I am VERY familiar with the Bratwursthausle - I knew one of the owners son well.
Several items on the buffet at Epcot are Americanized - a few years ago I went to find out about a certain cookie as someone requested a recipe here. It was something I had never seen (and I am very very familiar with German baking). The name was something rather generic; the servers at Biergarten also agreed that it was nothing authentic. Tasty, just not a 'traditional' item.
But I think that one can say that about most of the restaurants at World Showcase - the flavours/recipes are modified somewhat to meet the North American tastes.
I have been going to WDW since 1994 and never stepped foot into Biergarten until my Italian friend took me last year - I like some of the buffet items so I do like to go back, but if I want 'real' German cooking I have some of my mother's cooking....