The type of offset differences you are looking at with stock rims will have a negligible effect on performance as compared to aftermarket rims that can approach +10 or even 0 offset. Don't go mixing f/r with different offsets if you are trying to build a stable, predictable setup. More concentration on your tire pressure, toe and camber would have a much more noticeable effect on handling than pushing for lower offset wheels. But I would concede, as others mentioned... get as wide a track as you can, within reason... +35 is common. But amongst the highest offsets on an OEM car is +42 ... an offset offered on the OEM type R for reference and that setup is ideal for autoX and road racing... so both are great. Beyond +35, would put excess pressure on the outer portion of (some) rim's spokes which can possibly fatigue the rim faster than an OEM-esque offset.
Not that we are running 1 or 2 hour races, or even multiple laps so increased forces on the rim might not be such a factor with a 8 or 12 race schedule for the year... but ultra low offsets are for race cars, on race tires... guys that want to run 245's on a fwd because THAT'S how fast the circuit is
. Other than that... ultra offsets are for style... stay with 35 or 42 unless you wanna baLL OUt.