9 pas levels just gives you more options for power delivery, with a programming lead one can split the 9 levels in to two PAS group settings. For instance one could set 1 -5 for flatish terrain riding of low torque and high speed and then set 6 - 9 for high torque hill or off road climbing with high torque one naturally needs to set the speed amounts in the settings lower to benefit form the change also to help with the changes, adapt the front to take a double chain ring set up with 34t smaller ring and add a derailleur.
Sticking to the stock set up isn't obligatory so there are other options.
I'm going to go back to my old MK1 BBS01 with failed controller to reinvestigate why my external controller didn't work properly, once hopefully sorted I'm going to or hope to find a used long tail cargo bike and convert it with the BBS. I have ran the BBS with a double ring and derailleur with alfine 8 so know it works and is an option for lower gearing and higher torque.