Instinctual Stacking Descriptions are here.
The Self-Preservation Variant
Most people can easily identify this Instinctual Variant. Self Preservation types are preoccupied with getting and maintaining physical safety and comfort, which often translates into concerns about food, clothing, money, housing, and physical healthy, These issues are their main priority, and in pursuing them, other areas of their lives may suffer.
For example, we might identify this Instinctual Variant in ourselves or others by observing what a person would first notice on entering a room. Self Preservation types tend to focus on the comfort of the environment. Does the environment support their sense of well being? They are quick to notice and respond to poor lighting, or uncomfortable chairs, or to be dissatisfied with the room temperature, and they are constantly adjusting these things. They may wonder when their next meal or coffee break will come, worry if there will be enough food, or if it will be the kind they like, or if it will meet their dietary requirements.
When this instinct is functioning harmoniously with the personality type, these people can be earthy and practical. They apply their energies to taking care of basic life necessities- creating a secure environment, shopping, maintaining the home and workplace, paying bills, and acquiring useful skills so that the orderly flow of life will not be interrupted. When the personality becomes unhealthy, however, it distorts the instinct, causing these people to take poor care of themselves, possibly developing eating and sleeping disorders. They may stock up on too many things, overbuy, overeat, and overpurge themselves of unnecessary "baggage" of all sorts.
Less healthy Self Preservation types let themselves go physically, or they become obsessive about health and food matters, or both. Further, their normal practicality and financial sense may become distorted, resulting in problems with money and organizing their affairs. If the Self Preservation instinct becomes completely overwhelmed by personality issues, individuals may engage in deliberately self-destructive behavior, in which the instinct has the effect of turning against itself.
When the other two instincts dominate in an individual and the Self Preservation instinct is the least developed, attending to the basics of life does not come naturally. It will not always occur to such individuals that they need to eat or sleep properly. Environmental factors will be relatively insignificant, and they will tend to lack the drive to accumulate wealth or property, or to even care about such matters. Time and resource management will typically be neglected, often with seriously detrimental effects on their own careers, social life, and material well being.
The Social Variant
Most of us are aware that we have a social component, but we tend to see it as our desire to socialize, to attend parties, meetings, belong to groups, and so fourth. The Social instinct, however, is actually something much more fundamental. It is a powerful desire, found in all human beings, to be ilked, approved of, and to feel safe with others. On our own, we are rather weak and vulnerable and can easily fall prey to a hostile environment. We lack the claws, fangs, and fur of other animals, and if we did not band together and cooperate with each other, it is unlikely that our species, or we as individuals, would be able to survive. Being able to adjust ourselves to others and be acceptable is a fundamental, survival based human instinct.
People who have a dominant Social instinct are preoccupied with being accepted and necessary in their world. They are concerned with maintaining the sense of value they get from participating in activities with others, be they family, group, community, national, or global activities. Social types liike to feel involved, and they enjoy interacting with others for common purposes.
On entering a room, Social types would be immediately aware of the power structures and subtle "politics" between the different people and groups. They are subconsciously focused on others' reactions to them- particularly on whether they are being accepted or not. They are attuned to the notion of "place" within a hierarchical social structure, in regard both to themselves and to others. This can manifest in many ways, such as the pursuit of attention, success, fame, recognition, honor, leadership, and appreciation, as well as the security of being part of something larger than themselves. Of all the instinctual variants, Social types like to know what is going on in their world; they need to "touch base" with others to feel safe, alive, and energized. This can range from an interest in office politics or neighborhood gossip to world news and international diplomacy. We could say that the Social instinct is a kind of contextual intelligence: it gives us the ability to see our efforts and their effects in a broader context.
In general, social types enjoy interacting with people, although ironically, they tend to avoid intimacy. As with all of the instincts, if the person becomes unhealthy, the instinct manifests as its opposite. Unhealthy Social types can become extremely antisocial, detesting people and resenting society, and as a result, they may have poorly developed social skills. They fear and distrust others and cannot get along with people, while at the same time they are unable to disengage from their social connections. In brief, Social types focus on interacting with people in ways that will build their personal value, their sense of accomplishment, and their security of place with others.
When the other two instincts dominate in an individual and the Social instinct is least developed, attending to social endeavors and commitments does not come naturally. Such individuals have difficulty seeing the point of creating and sustaining social connections, often disregarding the impact of the opinions of others. Their sense of involvement with their community, at any scale, may be minimal. They often have little connection with people, feeling that they do not need others and that others do not need them. Thus, there may be frequent misunderstandings with allies and supporters as well as friends and family members.
The Sexual Variant
Many people initially want to identify themselves as this Variant, perhaps because they believe that this would mean that they are sexy or because they enjoy sex. Of course, sexiness is highly subjective, and there are "sexy" people in all three of the instinctual variants. If we wish to be one Variant rather than another, it is good to remember that the personality tends to interfere with and distort the dominant instinct. Thus, people of the Sexual Variant tend to have recurrent problems in the areas of intimate relationships. As with the other Variants, we need to see the way that the instinct plays out more broadly.
In the Sexual types, there is a constant search for connection and an attraction to intense experiences- not only sexual experiences but any situation that promises a similar charge. In all things, Sexual types seek intense contact. They may find intensity in a ski jump, a deep conversation, or an exciting movie. They tend to follow their attractions. (By contrast, Social types notice who is talking with the host, who has power, prestige, or who might be able to help them. Self Preservation types will note the temperature of the room, where the refreshments are, and what might be a comfortable place to sit.) Sexual types gravitate toward people they feel magnetized by, regardless of the person's potential for helping them or their social standing. It is as if they were asking, "Where is the juice in this room? Whose energy is the most intense?"
Sexual types tend to have difficulty pursuing their own projects or taking adequate care of themselves, because on a subconscious level, they are always looking outside themselves for the person or situation that will complete them. They are like a plug looking for a socket and can become obsessed with another if they feel they have the right person for them. They may neglect important obligations, or even their own basic necessities, if they are swept up in someone or something that has captivated them.
When they are unhealthy, Sexual types can experience a scattering of their attention and a profound lack of focus. They may act out in sexual promiscuity or become trapped in a fearful, dysfunctions attitude toward sex and intimacy. When the latter becomes their orientation, they will be equally intense about their avoidances.
When the other two instincts dominate in an individual and the Sexual instinct is least developed, attending to matters of intimacy and stimulation- mental or emotional- does not come naturally. They know what they like, but often find it difficult to get deeply excited or enthusiastic about anything. Such individuals also tend to have difficulty being intimate with others and may even avoid it altogether. They also tend to fall into routines, feeling uncomfortable if there is too much that is unfamiliar in their lives. They may feel social involved with people but strangely disconnected even from spouses, friends, and family members.
Source- The Wisdom of the Enneagram, by Don Richard Riso and Russ Hudson.
There isn't much out there on the Variants, so I figured I'd post this. I consider the Variants to be important. I'm personally a Sexual first and a Social second.