德國去意大利火車

德國和意大利並不接壤, 因此火車不可能越空而過, 從德國到意大利, 直接方法需要取道瑞士或奧地利才可以的. 這問題你可參考歐洲的地圖, 和德國火車公司的網頁 www.bahn.de. 應該會有足夠資料
至於從德國出發, 經瑞士 / 奧地利, 才到達意大利的列車是否必須另加費用. 這個可用 Eurail Select Pass 的 Adjoining Countries 的條例解釋 "This means that two countries must be linked by a direct train (not through another country) or shipping line which is part of the Eurail offer." 即是如果列車經過第三國, 你就必須補付第三國路段的車資 http://www.eurail.com/eurail_countries_select_pass

Germany to Italy, mostly you need to travel via Austria
My experiences from Munich to Bozano, Merano
I would say, count how many cities in one country that you gonna travel. If you only travel to one or two cities, sometimes, you can get local special tickets(e.g. like travel during non-peak hour or late evening)
Austria is a nice place too. Salzburg(with landscape), Vienna(flat, city feel).
Well, really depends on what you like to see. Maybe you already have your own idea, therefore, you chose the above countries to travel