this is a really hard question. questions.
i guess for me faith is a lot about what feels right, so that's a Fi thing. i was raised in a fairly strict, conservative religion and, while i appreciated the more "spiritual", congregational, and traditional aspects of it, i was never comfortable with so many of the rules being what i considered stupid and pointless. i didn't understand why religion needed to be so unnecessarily complicated - sounds like a bit of Te thrown in there - and i really just flat-out hated the idea of hell. the fact that my parents weren't particularly religious themselves was probably an influence as well - but they understood the importance of being educated in a religious tradition, which i am grateful for. it gave me both a lens from which, and an impetus to, begin searching elsewhere for other beliefs.
the way i got to my new place of faith was mostly by, upon completing the 8th grade at my religious school, going on a huge personal research project to check out other religions, learn about them, and determine where i stand. mysticism always appeals to me, because i think it touches on the important idea of experiencing the divine for oneself, without any mediation - and it encourages the cultivation of awareness. it also stands at the brink of being organized religion without succumbing to what i see as the pitfalls of religion by authority. that seems like a Fi-oriented thing. but then, i also really enjoy the stability and tradition of a religious community - Si-like things, i suppose. tradition is important to me, and not because it's the tried-and-true way, but because it's a way of connecting past to present and it encourages unity across differences.
so i studied bunches of religions, and loved elements of many of them, but none resonated with me enough to take on. i always had lingering ethical (Fi) or logical (Ti) problems. i finally have settled in
panentheism (theistic
monism); this is broad enough that it allows me plenty of room to keep exploring and integrating - what you said about Fi-Ne adaptability, i suppose - but i am also happy to have a term that succinctly gives another an idea of what i believe. i think what is most important to me is connection - i believe all is one and i believe connecting with one another is a good thing. it's rather Ne of me, really
at the core of myself i have one foundational belief that i have always had, which is that our existence is fundamentally good and purposeful - or, at least, that we can choose to make it such. i suppose everything else is built around that. and i do not know where that belief comes from - perhaps in part from the constant and unwavering love and support my parents flooded upon me from the moment i was born - but it makes sense both in my heart and in my mind.
anyway, i think that the religious search has been very good for me, in that my ethical system - my Fi construct, in a way - was constantly being exposed to seeing and weighing new ways of seeing the world. and, of course, still is. i think it also better helps me to understand how others can have certain beliefs, and why people of certain beliefs would behave in certain ways. i recently took several philosophy courses and they really forced me to look at my sense of ethics, too, which i had previously not really connected to my sense of spirituality. they are still not completely integrated, but i think they are more harmonious now that i have had to give them explicit thought and explain them to others. one of the difficulties about Fi is that it's all inside, and sometimes you
know that something is wrong but you're not immediately sure why. having to express my beliefs subjected them to logical (T) analysis, and some of my own logically contradictory assumptions became more clear; i think that was
really good for my own personal balance, to have Fi tempered. i've recently taken up the metaphor of Fi as a wild horse - to be befriended and allowed to run free, but calmed such that she is not destructive to herself or others. T helps. so in addition to "existence is/can be made good/purposeful", i have discovered that i operate off a few really core tenets such as "all life is important", "all humans should be loved and granted basic respect", and, since this topic is getting all too serious, "blue cheese is the scum of the earth."
i hope that begins to get at what you were asking.