@ OP
I kind of agree with others that a lot of people have given wonderful input in this thread, and while I can understand not being certain on which functions are preferred, or relating to elements of both types, it also kind of seems to me that you're waiting for a miracle answer that just makes everything snap into place so that you definitively 100% know without a doubt you're one and only one type. And... I'm not sure you're going to ever get that. Ultimately you'll need to seriously take everyone's input to heart, decide which you think is most valuable, and make a decision on which type/functions you think you PREFER. (mbti does not mean you are incapable of doing other things -- it's about *preferences*)
I'll share one brief anecdote, and you can take it or leave it, but I think it'll be the only thing I add to this thread.
Last weekend I was hanging out a few days with an INFP friend. We have quite a few interests in common, and had convos about books, 'bigger' more 'N' type life purpose/direction discussion, other sorts of things. Meaning -- ISFP's are quite capable and can quite enjoy these sorts of talks, and ISFP does not mean you can't be incredibly insightful, interesting/aware of theory and other such things, enjoy personal growth, and so on.
However one thing struck me as super interesting. At one point he was flipping through a book I made last year, filled with my photographs and writings of all of the things I've seen on hiking, natural history, flowers, birds, my describing the changing of the seasons in the mountains, what one sees and how things change from one week to the next, and so on. All very sensory, very *real* things. When he finished the book he put it down and his response was, "WHOA. I just had Lynn goggles on and saw the world as you see it." I found this funny / enlightening, as I quite honestly am surprised when people don't notice things I notice, haha. I then asked, well, what do you see or notice when you go on hikes? And his response was, well, I don't really notice anything. Which I found really strange -- it's like totally opposite of me. He then elaborated, saying, well, he guessed he paid attention to where he was walking, but.. he doesn't notice or pay attention to basically everything I notice and pay attention to. I found it extremely illuminating in terms of mbti/typology.
In a similar vein, while on the hike, I mentioned offhand 'These flowers were at peak maybe 10 days ago'. He was like..'Were you here last week?' (He basically didn't understand how I could know that) Then I explained no, but based on 7 years of hiking I'm aware of where all of the flowers bloom, the timeframe, how it varies from a wet year to a dry year, and so on, so I'm pretty certain/ I 'know' they were at peak about 7-10 days earlier, by how they looked the day I saw them.
In short -- conversationally INFP/ISFP can have a lot of similarities, but the SeNi for ISFP and NeSi for INFP is extremely different.
Maybe this will give you some insight into yourself.