Wow this comes up a lot.....
B mode, what it's for, going down hills. Regen, it will not ever ever ever add range. Energy comes out of the battery, over comes losses friction heat etc... gives x% to the car as kinetic energy. At cruise you use just enough energy to overcome all those losses. You then want to convert that kinetic energy back into the battery it will have to over come losses and give y% of x% back to the battery. This will never add range. If you want to go further coast to your stop. Period. Done. You cannot beat that method. If for example you are going to travel from 0mph at point A to point B where you are steady 60mph then at point C you start to slow to again be at 0mph at point D.
Regen:
Acceleration energy A-B. Cruise energy B-C, since you are amazing you capture the highest possible amount from C-D using the smallest amount of friction brake possible that the car will physically allow.
Coast:
Acceleration energy A-B is the same as above. Cruise energy B-C is less since you will have to start C sooner. Since you are amazing you start C at the perfect time so that with no regen and no friction brakes you arrive at D at 0mph in the exact same spot as above.
The net energy remaining in the battery from the coast scenario will always be higher because the savings you get from moving point C leaves more in the battery than regen C-D can ever put back in.
In B mode it is more difficult to coast, and more costly if you accidently use too much regen while trying to get a coast. In Eco mode it is easier to coast and you get more regen with a full lift off the pedal but no brakes. I'd estimate 75% of B mode. In Eco mode it is also very easy to modulate the brake pedal to get the same regen as B mode without engaging any significant amount of friction brakes (or even none). If you don't want to learn to feather the brake then use B but it's safer to feather the brake because your lights go on.
Since B mode is for going down hills it is designed to capture gravitational potential energy that if converted to kinetic energy would cause you to speed. Since we want to be good boys and girls (and also not have too much drag) we don't want to get too fast and end up using friction brakes to burn off that energy quickly when we notice we are in ticket zone.
What you can do is find out how to use regen and coasting to your advantage so that you ballance moving with traffic, getting to your destination in an acceptable time and using the least energy possible. In the real world with traffic lights as an example you have 3 things that happen most often.
1. It goes yellow and you're close to it, you hit the brakes hard. In B, Eco or D you'll put pretty much the exact same energy back into the battery.
2. It's red when you approach and you're far away, but close enough that it probably won't turn green if you keep cruising at your speed. To use B properly you have to maintain cruise and keep using energy then when closer you start to use regen. You will get to the lights quicker, if it's still red you now have 0 kinetic energy. If you coast as soon as you see the light you are now in a situation where you are using no energy, it will take you longer to get to the light so there is a greater chance it will go green before you get there and you then get to accelerate from said speed instead of 0 and you will use less energy to get back up to cruise. If you do end of stopping at the light same as above with A-B-C-D what you saved by coasting early will be more than you put back into the battery.
3. It's green the whole time, same energy in all modes.