The I/E is the easiest part of the entire MBTI to type.
If you spend a lot of time around people and get energy from it, you're an extrovert.
If you spend a lot of time by yourself and get energy from it, you're an introvert.
There's no need to overcomplicate the definition.
There's no mystical magical secret to the difference between ENFPs and INFPs. It's just that ENFPs spend more time around people and get their energy from it, and INFPs don't like being around and need more time alone.
There's a girl in one of my classes who I thought had to be an INFP because she was quiet and unassuming. And as I got to know her I went to her dorm to hang out during a writer's conference, and couldn't believe she'd turn down a single-bedroom apartment to be in an apartment with two other girls. To me, that's pure hell because I'd hate to have that much social interaction in my "house".
I later come to find out that this quiet, unassuming girl is actually an ENFP.
The only difference between us?
She gets her energy being around people (one of her reasons for taking the three bedroom over the single), and I get mine being alone.
There's no other difference whatsoever. Anything else different evolves out of our adaptations to the situations that these personality differences bring into our lives. There's no root difference other than that. It's just that the social nature of an ENFP manipulates their MBTI to be slightly different than ours, which is evolved out of our introverted nature.
Don't overcomplicate it. It doesn't mean you're any different than us. It just means you have more social experience and a more social element to your personality than ours, which actually loses energy in social situations where yours happens to be fueled by it.
There's no fundamental difference other than where our energy comes from.
In fact, in that same class, there was a girl who was much more confident when she spoke, and if she hadn't told me then I'd never have guessed she was an INFP. I'd have guessed her an ENFP over the ENFP that I thought was an INFP. The only way I could have possibly been able to tell is to have spent hours with her and see if I could notice a difference in her energy levels. If she got more energized, she was an E. If she got drained, she was an I.
No other difference.