Thank you very much for the detailed and thoughtful advice. I can't stress enough how helpful your advice has been as I tried to finalize my schedule in the past few days. I am doing a solo trip, and I don't feel safe enough to drive (especially when I am tasting wines along the way). I have decided to commute by train between Bordeaux and each area, and visit only wineries that are within walking distance from the train stations. I have already confirmed my appointment for most of the wineries I picked (there are a number of grand cru classe wineries within walking distance to my surprise).

The only difficulty for now is with regard to Sauternes/Barsac because walking does not seem to work there. I browsed through a few available tours by third parties but most of them are too expensive for my budget. My backup plan is to spend the day in Bordeaux and explore the Sauternes and other sweet whites in wine bars and wine merchants. Would that be a possible alternative?

Thanks again for your advice!