What distinguishes E from I in terms of Jungian theory) isn't a preference for socializing (although there is a resulting correlation) but rather whether your focus is predominantly outward vs inward. Extroverts are more effectively focused on what's going on around them.
Introverts are more effectively focused on what's going on in their mind.
As a result, Extroverts are better at "thinking on their feet" and Introverts require time to assemble their reply.
This difference dictates why an introvert wants to limit the number and quality of their social interactions.

Where the social interaction requires a number of predetermined responses like in a job situation, introverts and extroverts can appear similarly comfortable in their interactions. That's why introverts can appear to be more outgoing than they really are. (Also introverts who have personal experience in a given topic or an area of life can appear to really appreciate the social interaction.)

As conversations get more personal or otherwise require more thought, the introvert prefers to limit their interactions.

Then there's the theory that introversion exists along a spectrum which accounts for various degrees of a preference for social interaction.

You asked about personal experiences so I would put myself as a social introvert.
I have a mind that unconsciously remembers, processes, and stores social experiences and makes it easier to socialize the next time.

(INFP) But I have a limit in terms of the type of subject matter I prefer discuss. I like to talk to people about their experiences and what their mindset is presently as a result of those experiences. People who can articulate replies to that kind of conversation in an insightful way that expands my awareness of both themselves and of life arouse my interest. Beyond that very limited area of interest, I usually have nothing to say.

 

On one aspect, figuring out myself, my personality, my sense of style, and how I present myself can be very energizing to me. On another, I like being around certain people. Getting closer to them, telling them about myself (possibly my life story), and sharing my writing with them also energizes me. It's mostly about having a connection with people, and because of the praise and validation.

I think this is almost everybody. Even us introverts like to share our lives with people. We like to be around people who can appreciate those traits even if they are not exactly the same. Tribalism to a certain extent explains it. We all want to feel like we belong to some group, at least at certain times. Even if that group is on the fringe of the mainstream group.

To build on what UCP said above, I think many would differentiate introvert and extrovert by not only the number of people they feel comfortable socializing with at one time, but if they feel like they need some time to themselves after long stretches of socializing to "recharge".

Plus, introvert only plays one part. NPs usually view things different than SJs in what they want out of inner and outer worlds. Interesting dynamics happen when they mix as couples. Us highly introspective philosophical types mixed with highly task oriented types can either compliment each other or clash heavily.

Regardless, sounds like OP is a bit more I/E balanced, which will add some versatility in ways, always a plus.

 

The social draining probably has to do with always adapting with Ne which can lead us away from our natural Fi. The less we can be ourselves the more draining it is, but it can be kinda hard to gauge. Ni+Fi is more readily in tune with itself I think.