Day trips by train from Vienna

Have not looked at schedules for the places you mention but it is pretty easy to just hop a train and go in most cases. I took a day trip out to Salzburg from Vienna in December and most just hopped and paid on the train. Not all train operators will allow you to do this but another cases, I think it would be way to just buy at the station the day of. The down side may be that it is a few more $ than if you had pre-booked.

With the Hungarian rail site you can get the discount tickets the night before. But you can't use the Hungarian site to get from Vienna to Budapest. I just mention it to say check OBB to see if it's the same. Look up a price to Gyor for tomorrow and for 2 weeks out and compare.

AND, while I know you said day trips, Budapest does make a good day trip, but you get a ton more out of it and spend the night. The difference between the last train home and the first train home the next day is about 8 hours and in Vienna or Budapest you will be sleeping those 8 hours. Just that the evenings are so beautiful in Budapest.

Consider Bratislava.

You should add Brno to your list.

Which Altenburg are you referring to? Bei Linz or An der Rax?

Are you at least two people? If so, you should use the Einfach Raus ticket for your trips on regional trains. Einfach Raus tickets are puchased on the day of travel. https://www.oebb.at/en/tickets-kundenkarten/schueler-gruppen/einfach-raus-ticket.html

Longer distance travel, like Budapest, is best purchased in advance for a specific train to save money.

You said you are interested in architecture, then there is the "Villa Tugendhat" in Brno, an outstanding landmark created by Ludwig Mies van der Rohe, having gotten unlimited funds from the clients to build it.

Eisenstadt, home of the Esterhazies and Haydn.

I spent a week in Vienna around 1975. Everything was black from centuries of smoke and war. Returned last Nov for 2 days on a river cruise and there has been a transformation. The physical/ appearance of the city makes it a new ball game ,so I thought I'd go bark for a longer stay and see the new Vienna. I found a really good air and hotel package for two weeks, which I suspect is a bit to long for a Vienna repeat, so I planned some day trips to some attractive places I'd never been to. So, per the suggestions to spend more time in Budapest, already been there for 5-9 days. I have 3 specific neighborhoods I want to explore,so one day is enough.

Bratislava: been there 3-4 days.

Brno: Too far for a day t0rip from Vienna.

Eisenstadt: Been there (2 days). Had a hotel room overlooking Haydn's house. Met Gorbachev. Best sight: the inscription on Haydn's tomb.

Altenburg is the one near Horn. It seems it requires both train and bus to get there. I might rent a car.

I cannot buy tickets in advance because I want to go only in good weather, and that cannot be predicted more than a day ahead and there isn't enough travel to justify a Eurail pass or such.

Brno is 1.5 hours by train. Much closer than Budapest and about the same as Gyor. I suggested Brno as you seem to be into architecture. I think 1.5 hours is a very doable day trip.

A Eurail pass would be ridiculous as regional travel is super cheap with an Einfach Raus ticket.

Based on the impact Vienna had on you on your trip in November, you will love Budapest.

Emily

You're right on Brno. I know why I missed it. I've looked on several occasions at Praha-Brno and decided it was to far for a day trip. I forgot that Wien is not Praha. Thanks. I'll do it, weather permitting.

Can you put these in order of preference? Gyor, Sopron, & Brno for street scenes & Baroque Churches?

I haven't been to Brno, but between Gyor and Sopron I pick Gyor/Pannonhalma Archabbey before Sopron.

If you go to Wachau Valley - before or after visiting Melk Abbey -, don't miss Krems.

Krems has a beautiful, extremely well preserved historic center and the "Kunstmeile" (art mile / museum mile) with the spectacular new building of the "Landesgalerie" (state gallery).

http://www.krems.gv.at/About_Krems
https://www.kunstmeile.at/en/homepage

I'm planing a 2 week stay in Vienna in November 2020. [...], so I want to go in good weather ...

Don't have exaggerated expectations about the weather at that time of the year. :-)

The Christmas markets open in Budapest on the second Friday in November .... something to consider.

For beautiful architecture, listen to this https://youtu.be/0nd9DuDGCz0

The Christmas markets in Bratislava are my second favorite after Vienna. If you plan a night at the Radisson Blu you can literally walk out the front of the hotel into the market.