Regarding the warranty, I think would depend on the failure point. If it's related to the anything connected to the exhaust, they probably will not honor it. However, if the failure is in a different part, I image it would be hard for them to claim it's not covered.
You can find videos that...
Yes, the NISMO Titanium is made in Japan, by special order. I could immediately feel the difference. The car feels more responsive and less constrained. The sound is refined; not too aggressive.
^ That's where I bough mine from. I don't find the partial carbon inserts attractive, so mine will be leather / perforated leather, with a flat bottom.
I am replacing the OEM RZ34 NISMO wheel with a custom-made one. I have done that as well in my Z33, so I took it to the dealer to ensure no issues would occur with the airbag module.
My Z33 wheel looks like this. (Picture from the vendor)
They stick out more than the factory tips, which is a very good thing. I always thought the OEM exhaust was not proportional to the rest of the NISMO bumper.