Yeah, I hear you. We were there during the Tour de France in 2024 and I'm amazed I didn't kill a few cyclists on back roads. And I totally agree on the car size - had a big ass wagon last March in France because I brought my skis and too much ski gear. Parking that thing was absolute misery. I hated it. I really need to get my family to pack lighter so we can get smaller vehicles when in Italy. And, yes, the drop off fee to another country is absolute ass. I've always avoided doing a one-way trip from one country to another.
Can't help you so much with Austria and Germany. My sole experiences in Austin were skiing in the Oetztal Valley. I've passed through Innsbruck before and that looked nice and to get from Innsbruck down into Italy/back is super easy. Mind you, I actually look forward to driving in Italy. I love it. I mean, parking can suck but I love the energy of driving around Italy. I haven't taken a train in 20 years. Anyway, you could do Vicenza or Padova or even something like Verona so that you are near Lake Garda. On the train, how are you pricing it out? First class? Second class should be way cheaper and you can listen to someone talk on their cell phone for the whole journey.
I've found that when we don't have our own car (if we didn't drive up) then they usually give you WTF they want and tell you, "oh yeah, this one's fine" and then you just kind of figure it out. I've driven over Mount Rose Summit Pass and Berthoud Pas in brutal blizzards, both in crappy sedans with suspect tires. I would say just go nice and easy. One upside (of many) of skiing in places in Europe is usually rental car snow tire requirements. Most times they are legally required to provide them to you at no charge.
I will advise what I usually do... don't move around too much. Pick a couple of bases and stay there and take side trips. I swear some people's itineraries just wear me out.
...and in the end I was disappointed to see the announcement, even before I knew how he handled it. He could have had a promising role here in Austin. Welp, don't let the door hit you on the ass on your way out.