My oil filter kit that I bought at Lexus has only one "o" ring. The "pinned" how to oil change in this forum shows two "o" rings. My IS 250 is RWD and the car shown for example is AWD. Is there a difference in oil filters for these two models?

Yes! There is a difference. I also have a RWD and was issued an AWD filter element by the Lexus parts manager last year. Upon checking the box before I paid for it, I discovered it had addition hardware that I didn't receive for my prior oil changes. The parts manager quickly realized he had given be an AWD filter element and swapped it out. Not sure where the extra o ring goes or whether or not the filter elements are different. I'd just insist on getting the right part for your car.