Re: 2 basic tire questions
Class Bs run on light truck tires which carries the LT designation. I don't know what you mean by standard but they should at least be LT regardless. The tire dealers like Tires Plus, Sears, Discount Tire, etc. all have search functions for you vehicle to determine the proper tire size. As for the 80% in the driveway, that is not the part that counts. It is the other 20% on the road. Generally, the higher mileage warranty tire is going to cost more and for them to warrant that tire it is most likely a better tire whether the first mile you drive it or the last.
You just have to look at your annual mileage and how long you plan to keep your B to determine how much you will be willing to pay. I put 56,000 miles on my B in 3 years. I already had to buy new tires because the original set lasted just about what they were warranted for at 40,000 miles. I upgraded to a top of the line 70,000 mile warranted tire. I'm getting much better tread wear now and a little more peace of mind out on the road even though I doubt I will drive 70,000 miles on them (but someone will). But, I already know with my driving habits a 40,000 mile tire won't cut it. My tires sit for about 67% of the time.
Another factor is don't buy a warranted tire with more mileage than you might put on them in 8 years or conservatively 6 years. Even if they still have decent tread they will be approaching their useful life and be subject to blowouts.
2021 Advanced RV 144 custom Sprinter
2015 Advanced RV Extended body Sprinter
2011 Great West Van Legend Sprinter
2005 Pleasure-way Plateau TS Sprinter