For overlanding, per se, 32's are about all you need. If you can fit 33's without trimming and lifting, fine. Running anything larger than stock is going to have an immediate impact on driveability including fuel consumption, available power, alignment management, speedo errors, additional unsprung weight, and so on.
So it depends on what you really want to do with your vehicle. Overlanding and more recreational off-road driving are not really the same thing. Most of the roads and trails covered in overlanding can be done in stock trim, so tall tires are not generally needed, nor do they necessarily add anything to your ability to enjoy vehicle-based exploration and camping.
If you go back only about 15 years, you would find that most folks thought 31x10.5 tires were HUGE, and every trail on the planet was covered with tires no larger than that. I crossed the Talkeetna Mountains in central Alaska in 1997 on 31x10.5 BFG MT's on a trail that had up to that point never been done with a street legal vehicle. It was not a problem.
Personally, I feel tall tires are irrelevant to overlanding, and that for the purpose, a narrow 32 inch tire is about all you will ever need. If you are now running 31's and not having problems getting where you need to go, I would not change size just to change size.
