My wife and did this trip as a private tour. We stopped at three monasteries, toured Sremski Karlovci and had two wine tastings. It was a good tour and we enjoyed it. The guide spoke good English and told us a lot about the area. We also hired them for a transfer from Novi Sad to Belgrade which worked out well.
The only issue we had is that they aren’t good at working up custom tours. They have a menu of tours and stick with them, even for private tours.
Prices were reasonable.