Typically, teeth treated with root canal therapy should recieve a crown if they are located in the back of the mouth.
Some front teeth can simply be filled with a filling. The determination is a clinical one that is made by the treating dentist and is specific to the circumstance leading to the root canal. If there is a lot of healty remaining natural tooth, a crown may not be necessary on a front tooth. Most root canal treated back teeth do need a crown on the other hand.
The internal whitening is for teeth that have been traumatized. Often blood from trauma can enter the tooth and cause discoloration in which only internal whitening can correct. If the tooth will recieve a crown, correction of color may not be necessary because the tooth in question will be covered by a crown.