I have no idea what B mode is for honestly I'm just trying things on this trip haha. I think it's more regen although on the highway I don't think it matters.
Forgot to mention I keep the e-step on all the time so just fyi.
D mode is no regen. B mode is regen, e-Step or e-Pedal is regen. Econ mode is regen and slower accelerator response. I don't know about Sport mode.
Regen modes always improves range, even on a flat road. Every time you let off the accelerator, the motor charges the battery. I once regained 27miles with my 2020 Leaf when coming down a long mountain in VA.
You can see, for yourself, exactly what's happening with regen and the different modes. Notice the circular power gauge, it's essentially a current meter. The bars from 10 o'clock to about 4 o'clock show current into
the motor. The bars from 10 o'clock to about 6 o'clock show current from
the motor into the battery. You can change modes while driving and see for yourself.
It's theoretically impossible to get a longer range without regen. Without regen, slowing down puts energy into the air and heat into the brakes, rather than the battery.