2011 sti I put on Rota Grids 18x9.5 front an rear with 38 offset. It is aggressively wide, flush with fender with stock camber. If you go to 30 it would need more camber and 20 would be crazy amoun of camber. Running stock tires 245/40/18 stretched but not crazy stretched. But I already rubbed curb as tire is not bulging to protected rims. I would say for lowering I may have been better getting a less aggressive offset as now the tire is under the fender where it can have rubbing issues. Stock suspension now and fenders are not rolled, it doesn't rub. I will report back when I put coil overs on in the next month.
Flat black actually looks good.
You need 5mm spacers in front for brembo clearance.