they are refering to the diameter of the sport rim/wheel

tyre are typically measure by the numbers like 195/60/15. 195 denotes the width of the tyre, 60 denotes the thickness of the tyre measured in the ratio to the width (this case 195), and 15 means it will fit 15" rim.

it does effect.. but nowadays people are fond to fit smaller width tyre as to get the stretched effect like the japanese do.. its called "hapiri" style.. usually wider rims is nicer..

your stock rims is 15' and you want to change to lighter 15' rims. of course, more advantage there

the taiwan vs japan rims issues focus on 2 points. weight and strength.

japan rims are known for their strength and of course weight
while taiwan rims are light too. about the strength, well, depends on the brands. some cheap brands from taiwan of course easily bent which is not good .

but to answer your question, in terms of car perfomance, taiwan and japanese aren't much different. in terms of rims strength, japanese wins hands down.

but me and my family have been using 2 brands of taiwanese rims and both are good. Advanti racing and Kspeed. both of them served all of us well for 10 years(advanti on kia carnival), 6 years(kspeed on wira), 1 month (advanti on viva).

the 899? the advanti ultralite version is it? i've been using that too for my viva  . hoping for it to last long just like the old advanti on family's kia carnival.