Personally, I think that the best way to play is to avoid directly the powerups, as much as possible.
One takes out random lines, thing that is a problem
One makes it go faste, that is something bad
One give some extra points, but the risk that it goes wrong is too high. You will make more points avoiding the orbs.
So I suggest you to give some feedback to the player regarding whose orbs are the good ones.
At the same time, some visual effects showing the effects of the orbs will be appreciated. The first time I saw one missing line I though it was a bug.
Anyway, good tetris