Both the King and Lover protocols can have an effect on libido. King users generally report an increase in energy, better sleep and improved gym performance as well as increased confidence and assertiveness. Lover users report overall increased libido and blood flow during performance.
If you're looking for something to improve your T levels then King Protocol is the best option, if you're just looking for increased libido/blood flow then you should go with Lover Protocol. They share some aspects such as improved libido, but the main result of King Protocol is optimized T levels (which may have an effect on libido for some users).
More information on these protocols here:
Some patients take both together, as they work together synergistically. You can always consult with your clinician once you sign up and they can assist you further with deciding which protocol is the best option for you.