If you tow I recommend helpers, but they are not a must have if you aren't. I don't tow, and I have them. Not sure if they were really worth it, but people claim they are worth buying.
The NNBS trucks can get away with 4/7 and no notch. Do you need it? No. But if you have rough roads or shit shocks you may hit your frame. If you ever plan on going lower you will need a notch. My advise, do it. I was against it, went 2/4, and decided I wanted lower, and then notched!