A friend and I were talking about where exactly different levels of narcissism would fall on the N-spectrum. Of course narcissism (or any psychological topic) isn’t an exact science so giving the different levels numerical values seems a little silly, but in my mind this is how I view the different levels on the spectrum, starting with a Baseline of O (on most narcissism spectrums, “healthy” narcissism is at baseline) and the transition to NPD at around 5, which is smack dab in the middle. Narcissism becomes pathological (causing the person or others problems) at around 4.
Please note these are just my own subjective ideas.  I’m a geek who likes to classify things.

The Narcissistic Spectrum according to Lucky Otter

9-10:
Sociopathy: A person at this level is almost indistinguishable from someone with ASPD (antisocial personality disorder), but an NPD sociopath is more concerned about image or obtaining supply than a pure ASPDer. Most cult leaders fall here. (Psychopathy appears similar to sociopathy in behaviors, but describes a condition that a person is born with instead of one that was acquired; many psychopaths were never abused and were always like that, but sociopaths were made).

8-9:
Malignant Narcissism: A person at this level has severe NPD with antisocial traits. A person at this level will show more emotion (usually rage) than a narcissistic sociopath. Usually fits all the DSM criteria or most of them.

7-8:
Severe NPD: Not malignant because there is no sadism present, but person is still highly dangerous and manipulative. Fits most or all of the 9 criteria and symptoms are severe.

6-7:
Moderate NPD: A person at this level may be barely tolerable, if contact with them is casual or seldom. Fits more than 5 of the 9 criteria.

5-6:
Mild NPD: A person at this level fits 5 of the 9 DSM criteria for NPD but symptoms are not too severe and they may have moments of acting like a decent human being. NPDers at this level may occasionally respond well to therapy or seek it out.

—Pathological—

4-5:
Narcissistic Personality (Destructive Narcissistic Pattern disorder or DNP):  A person here fits fewer than 5 of the 9 NPD criteria in the DSM but has at least three.  Symptoms may not be that severe and the person at this level is more in touch with their true self and may seek therapy.  They usually have the capacity to feel empathy but it’s limited.

3-4:
Non-Pathological Narcissistic Personality: Your garden variety self-centered jerk but may genuinely care about those they love.  Not particularly dangerous. Has moments of insight into themselves or empathy for others, especially their loved ones.

0-3:
“Healthy” narcissism. Most normal people can be found here.

O (Baseline) and lower:
People down in the negative digits might as well be wearing a “KICK ME” sign. They are almost always victims of narcissists and sometimes even normal people give them a hard time or take advantage of them.

The simplified spectrum. Psychopathy does not belong here at all.

Covert (“fragile”) narcissists may be found anywhere on the spectrum, but because their narcissism is more hidden and arrogance and grandiosity may be absent, a covert narcissist at any level is harder to identify. They may appear to have BPD, Avoidant PD, or Aspergers Syndrome instead (these are the three disorders most often confused with Covert Narcissism).

High-functioning (successful) narcissists are more likely to be found high on the spectrum, and sociopaths are often extremely high-functioning. There are many sociopaths (and psychopaths, who were generally born with a different brain structure and may not have been abused) in politics, religion, and heading huge corporations. Sociopathic traits and most NPD traits are generally sought after in the higher echelons of business, politics and entertainment. A person with just the “right” combination of antisocial behavior and arrogance, entitlement, grandiosity, and fake confidence can be a devastating adversary or competitor, and they will have no scruples about crushing you into the ground to achieve their goals.

Most high-functioning narcissists tend to be the Grandiose (classic, or overt) type that best fits the DSM criteria.

Covert and overt narcissists all have the same disorder, but for most, one form or the other is dominant. That said, they can and do switch back and forth in the same person. I think temperament is partly to do with whether someone is overt or covert (the more timid or fearful types leaning toward covert narcissism), but I also think circumstances (such as a sudden loss or gain of supply) can cause a switch from overt to covert or vice versa.

Low-functioning narcissists are much more likely to be covert.  They tend to receive less supply than overt narcissists, so their false self is weaker (the “deflated” false self, according to Masterson). Because of their discontent with their lives and general lack of success, covert narcissists are more likely than overt ones to seek help. If a covert narcissist suddenly begins to receive a lot of supply, they can become much more overt-acting (grandiose, entitled and arrogant). If an overt/grandiose narcissist suffers a huge loss of supply, they can sink into depression and become covert (at which point they are more likely to seek help).