This is an incredibly difficult bending style to master, and in fact very dangerous.
The capabilities of Energybending are not well understood; what is known is that bending a person's life energy can impart them with knowledge instantly or remove one's bending completely.
Aang energybending the Firebending powers out of Lord Ozai
The danger of this technique is shown when:
At first Aang's spirit [is] nearly enveloped by Ozai's, but at the last moment, his spirit took over and covered Ozai, removing his Firebending.
In which case:
If the bender's spirit is even slightly weak, bendable, they will then be infected by the spirit of the one they are bending. As a result, the bender can be corrupted and even killed.
If Aang had a weaker spirit, which was nearly the case, he would have been overwhelmed by Ozai's and corrupted/killed by his power.
As such, Aang could not have given Toph her sight, but he could have taken her ability to see via earthbending. He could even share her unique knowledge of earthbending to others. I don't see anything in cannon to say whether or not her could give non-benders bending powers, or give someone a different power. However given the Lion Turtle gives Aang the power of Energy bending, when he had no knowledge of this technique before, it possible the same could apply to the other mundane forms of bending.