Looking into taking a train from Vienna to Frankfurt - apparently there are ICE trains for the route, but I assume these are not the high speed type since it takes like 7.5 hours with just one train change. Which routes have the fast trains?
ICE = fast trains. There are several DIRECT trains for this route, but they still take nearly 7 hours. It's a trip of more than 700 km, and all trains make stops along the way.
Find all options at the DB itinerary page.
This is the route that goes through Linz and Passau, count about 7.5 hrs. Now there's another way if you time it right changing only once in Munich. Take Wien West to Munich Hbf on the Railjet train, then Munich-Frankfurt Hbf. on the ICE. I've done both ways. If you want the straight shot, then it's through Linz and Passau on the ICE.
For a trip of that distance, I'd look into flying. Check Skyscanner for options: http://www.skyscanner.com/