In a corner, the rear sway bar will increase the difference in loadings on the rear, and thus cause oversteer.
With an IRS, under straight acceleration, ideally it would do nothing at all.
With a live axle under straight acceleration, I'm thinking the only way to counter the load transfer left to right or right to left, will be either asymmetries, or to try to transfer the torque back to the front (where, at this very moment, there is an equal and opposite torque acting! yay!). I'm not sure... but I think the only way to do that would be with a stiffer chassis and then maybe also more roll hardness in the rear, less in the front? The idea being to make the front suspension need to deflect a whole heap to react the torque (hence softer front roll hardness), then the stiff chassis helps transfer as much of that deflection as possible to the rear, where it puts pressure through the springs on the rear tyres, and hopefully reacts some of the torque through them, which should reverse some of the load transfer.