there's a lot of variations and it does depend on the culture. but definitely 1-2 days produces a more sour and i wouldn't call it thicker, it tends to separate more into curds and whey, and the curds are not really fluid, but if you shake it up it's still more liquid than 12 hour fermented.
24 hours is definitely better. more bacteria, less casein and less lactose.
Sour is fine. In fact it means it is better, because of what you said. More bacteria, because these are good bacteria for our body. Traditional yoghurt is sour too. It is the last 20 years or so that big companies that sell yoghurt made their yoghurt less sour because they wanted to sell abroad, where yoghurt is not a traditional and well known food. Still what you describe sounds more than kefir or ayran than yoghurt. Which is perfectly fine. I like all of these things
