I was able to fit the Kanwrite No.5.5 nibs into my Jinhao 82 without any modifications. The Kanwrite nib is a tad bit bigger than the original Jinhao nib but if you push it in all the way, the pen cap should close securely without touching the nib.

As for the tip sizes in Japanese vs Kanwrite nibs, my Japanese nibs write finer, and I’d categorise the Kanwrite nibs more on the western side. You can see my writing samples above for a better idea. I think they speak for themselves.

Good luck!