both jump 2 (power jump), and jump 3 (hover jump) work if you hold down the jump key, unlike jump 1 (multi jump), which you use when you hit the jump key in mid air. If you just press the jump key, and quickly release the power jump acts like a normal jump, which is not an air jump.
Hover jump's mana cost is deducted right after you you use it, and more mana gets deducted after the bar goes down.
Side Note, Power Jump stops your movement when you start charging it, but you can still squat down for extra boost.
Reminder if you have no mana, then pressing the jump key is just gonna do a normal jump (which is not an air jump). You can still hold the jump key for Power jump even without mana, and it is going to deduct mana as soon as you regenerate it.
"In my opinion the jump bar should be different color than the mana one"
I will keep that in mind when I am gonna be replacing UI.