About matching a load to a Tx line

Matching a load to a Tx line using a stub, for example, does it make max power to be transferred to the load or just to eliminate reflections?.... the section between the stub and the load still works in standing wave mode??
How may I calculate the power at the load after inserting the stub in order to make a comparison?

To calculate the power at the load have to find the mismatch loss:
ML [dB] = 10*LOG(1-Γ2)

Mismatch loss - Wikipedia, the free encyclopedia