Hi i agree with most of what john is saying even with road tyres ,an even temp means even tyre wear ,f you have a tyre capable of more girp why not use it.Sure good times can be got with a really wide tyre working on one side but it is capable of even better times using the whole tyre.Road tyres ,while not like slicks, still need to get to temp,lower pressure more heat simple as that.
As far as stiff sidewalls i agree stiff is good for 2 main reasons ,they have less flex and this lets us run lower pressure for more heat, but still let you increace pres if they get too hot.
Many years ago i raced a xu1 style torana ,I had no money and everything was on a budget ,so we did what we could with normal street tyres .everything was seat of the pants,we had thin sidewals ,so we would stretch195 tyres on 9" rims and played with pressures to get the best compromise between grip and flex.Doing this can teach how important tyre pressure is.but back to the first string wide soft tyres can be great on the road dry but over wide tyres no matter how soft will be bad in the wet.
col