Smaller clutch = more low end
Bigger clutch = more top end
bigger spur = more low end
smaller spur = more top end

What do you want more top speed or more low end torque. You cant do both. If you want good off road then change the tires. You can play with the gears till you turn blue and it wont matter off road. Go with some Moabs, Mashers or Yokohamas for off road.