If I correctly noticed that there is no bonus from titan orb for killing Titan as it gave 10 titan stone it remains to give although I pumped several lvl orb
It doesn't change the amount you get in the reward (Meaning when you click on the Titan head). It gives you the chance for additional drops on kill. TitanOrb levels will then increase the amount further.
 "IF2"){kind=icon}
 "IdleFighter"){kind=icon}
Fire Boss drops Titan Cores which will Auto loot on death, so even off stage you should still have collected the reward