The Commander Pro is more a hub and is designed to manage all Corsair devices like the Lighting node pro.
So say you have the following:
- H115i
- RM650i
- LL120 fans with two lighting node pros
All three these use a USB header (two for the lighting node pros). The Commander will allow you to connect the PSU, cooler and both of the lighting node pros into it thent hat into a USB header and then all be controlled, if they have RGB or other controllable features, by the iCUE software.
So to get the LL120s to work, no you don't need the Commander Pro. They will light up and will be configurable by the iCUE software with just the Lighting Node Pro plugged into a USB header. The Commander Pro would only be beneficial or needed if you have more devices than USB hubs on your motherboard.