We can see all the variations in human types in planetary terms. We can understand all human problems according to the energetics of the planets. We can understand all psychological problems according to the functioning of the planets on a lower level, and spiritual growth as their function on a higher level.
For people who have two planets of equal strength, a mixed type will emerge. For example, a Sun-Moon type will have a strong personality, both in its active and receptive, solar and lunar sides. A Mars-Jupiter type will give a Jupiter-based expansiveness to the Mars work and action principles. A Mercury-Jupiter type will have an expansive but detailed and strong intelligence. A Mars-Venus type will have a strong sexuality, passion and vital will.
Sometimes higher and lower planetary influences combine as well. For example, a person may have a higher Jupiter influence with a lower Mars energy. They may have much expansiveness, faith and a philosophical disposition but allied with a lower Martial will to impose it upon others.
Secondary planetary types also exist. A person may be primarily Moon but Venus secondarily, for example. They will have a strong lunar, maternal or receptive feeling nature, yet with a significant need for affection and beauty, Venus traits. Thus, we can understand the differences between people of the same planetary type by what planet is second in their nature.
Sometimes a weak planet characterizes a person - they can be seen by the planetary strengths lacking in their nature. For example, if the Moon is weak in a chart, fear, moodiness and an inability to relate to people will characterize the person. Such an influence may be so strong that it is best to aim at correcting this weak planet rather than dealing with the planetary type.
Most often, however, weakness of a planet is caused by another planet being too strong or pronounced. For example, a strong or prominent Saturn and Rahu and their malefic influence are usually behind a weak Moon. Hence, Saturn or Rahu types usually have weak Moons.