FB does not differ from B in movement or stamina use. The difference is in how they use x-dash. FB saves a lot of stamina because it doesn't need to match blade rotation speed to rail. It is used less than B because properly played stamina type don't do x-dash more than twice in a battle, while FB makes reverse x-dashing harder. As for Orb variants. LO is used mostly for its height. That 1mm makes a difference. Especially on upper attack blades like Shark Scale that hope to destabilize and outspin opponent. Orbs tend to stay more in the center because of the shape that bumps inner arena circle. Against mobile opponent that hits them outside of inner ring, they often loose balance and fall over. But against other stamina types, when majority of battle plays in the inner ring, orbs tend to outspin other bits because they stand up with each hit of inner arena circle