First you just can not just randomly change tires, you need to find out what came on from the factory and stay with that or you will do damage to the 4wd.
Changing width of a tire also changes it's RC so again it will hurt the 4wd system.
I'm not sure on your model, but most models require you to change rims for bar tires.
I have a BX22, and when I purchased it new, I also purchased a set of bar tires with it, along with some other accessories that I wanted. On my tractor, the original tires were made by OTR, and both the bar tires and the turf tires used the same rims. These original tires and rims (wheels as Kubota calls them) are still in service on the tractor. The reason for their replacement is that they are cracked, and are loosing air.
The original front wheel is part number K2561-18180, which has been superseded by part number K2561-18190. Both of these wheels are 8"x7".
The rear wheels are part number K2561-17180 which has been superseded by part number K2561-17190 and are 12"x10.5" for both the turf and bar. The only thing that I have modified on my rims are the valve stems. I replace the rubber valve stems with metal bolt on valve stems, because they don't deteriorate from the weather, nor do they get torn if something should snag them.
Since you brought up the wheel sizing, I decided to check the wheel size of the BX23S, and I find that it also uses the K2561-17190 wheel in the rear for Bar, Industrial, and Turf tires and is the same wheel that was installed on my BX22 in 2004. The front wheel is part number K2581-18180 (10"x7"), and like the rear, the same wheel is used for Bar, Industrial, and Turf tires.
The front tires haven't changed size with the exception of the rim diameter went from 8" to 10", and since both tires are the same size, with the exception of the tire hole in the middle, I believe that the rolling diameter of both the 8" and the 10" tires are the same. I will confirm this before moving to the 10" tire. What I have found is that the selection of 8" tires is very limited as compared to the 10" tire. An example is the industrial tire isn't available in the 8" wheel diameter, but it is in the 10" wheel diameter.