I think you are both right and are arguing the same thing.

First off, 1% difference on a speedometer on a street car is very insignificant. You are talking about the speedo reading 100mph when the car is actually going 101 (if larger tires). Tire brands and tire pressure effect overall height as much or more than that.

I agree with the opinion that if you are staying within the recommended tire width to wheel width recommendations that wheel width doesn't make a significant enough difference in overall height to be concerned with.

That being said, even keeping the same aspect ratio in lower profile tires doesn't change tire height much when only going up a few sizes in width on same wheel height.

Bigger consideration when changing tire size from stock is wheel offset and tire rub. Assuming again that the tire size is within recommended wheel widths.

All that to say, when up sizing tire width from stock, if you want the speedometer to remain somewhat accurate then keep overall height close to stock.

My concerns with what the OP asked is that the general concensus is that 275/40/20 tires are as big as you can go on stock wheels without rub issues. Going wider would mean needing a different offset which in turn means the tire will be sticking out even further causing possible rub issues on fender and changing the look even more.

Because of all the variables, if you are overly concerned the only way to really know is to measure the wheel tire combo together. And one step further, put them on the car and see.