I sauteed the onions and apples for the cabbage in grapeseed oil, mostly just because that's what happened to be next to the stove at the time. Not that I think about it, I should have just used butter. Everything is better with butter. Nothing is better with margarine. Although 90% of the time I cook with olive oil.
I'm talking about one of these mandolins, not the musical instrument. The answer to what I would have done with it is, "Probably cut the tips of my fingers off."
You can absolutley use white wine instead of vinegar, just add a squeeze of lemon juice since wine doesn't have that vinegary bite you want. I actually used apple cider vinegar but I said white vinegar in the recipe because that's how it's normally made.
Lemon is a must for schnitzel. It makes the whole dish. I squeezed half a lemon on my schnitzel.