Bear in mind online with tire wear/fuel consumption enabled, the tire wear and the amount of fuel in the car can change the handling. I often test my replica online at Tsukuba with fuel/tire wear on very fast, and I can drive similar lap times as offline, when I fit fresh tire and fuel is about 25% in the tank. The handling is very close to offline in this state.
There's also a difference in handling offline when comparing SS to RH, especially on road cars when not fitted with chassis rigidity. The violent snaps of RH tires can be amplified when running low or zero camber and toe + low lock/near open LSD + relatively soft springs.
I see a gulf in car balance alone when fitted SH and SS to Ford Falcon AU XR8 ( race car ) compared to RH at High Speed Ring seasonal ( GT500 ) that currently runs. This is with no tire wear, and adjustments may be necessary to suit the tire characteristics.