We had a wonderful stay at Tanya's. We were 3 people and still felt that the flat was quite spacious. The only issue we had was that there was no wifi during our stay (due to construction occurring close by), which was quite inconvenient. Luckily, Vienna is easy to navigate and it encouraged us to explore the coffee scene. That being said, while the flat may not be considered central, it is definitely walkable to many attractions (~15 min to Belvedere palace, ~25-30 min to most attractions in city centre). For those not too keen on walking, Tanya's flat is perfectly situated in terms of public transportation (barely 2 streets away for the tram and several streets for the underground) and/or an inexpensive uber ride (~4-6 euro). There are also several options for food nearby, as well as a grocery store.
Overall, Tanya was a great host. Easy to communicate with, flexible, and always available if we had any questions.