Reading - Ne & Fi. Just a note, I'm no expert on the functions, but I will use a general idea of the functions to explain my understanding of the connections between them. I can't see the functions as separated into activities, because each activity is likely inclusive of many processes occurring at once, similar to what Ren mentioned.
What you describe
@Ginny in your discussion of reading and Fe + Ni, is something I experience almost exactly and I am supposedly the opposite in functions. This is why I'm not sure functions can be typed to specific mental activities. I think specific mental processes may reflect a particular function orientation if the entire focus of that activity is on one specific task but I don't think we always or maybe know for a fact what function, whether Ni or Ne, we are using when you apply a particular mental activity to a concept or process. For example, I can look at a film and discuss the scene, setting, emotion or mood, and use both Se, Ni, Ne, etc. But I could be wrong about the function I am using to perform that process. Another example, Fi is an analytical function. It processes things along with Ne through the lens of values and possibilities. But Fi can also be Ni-ish in that it can pick up on insights about selves or others in how it analyses something in a story read or movie watched. Yes, this could be self projecting, but it could really be thoughtful insights afforded by the combo of functions picking up on different things. And then it's no longer a simple case of Fi or Fe, or Ni or Ne. More are combined to notice or process what is seen.
Another example, Se is often associated with enjoying the outdoors or processing things through the senses, and considered a highly visual function. But when I am outdoors, taking a walk in some type of nature, yes, I may like the seeing the green and enjoying the fresh air, but maybe the experience I have is due to the introverted aspect of the walk including the alone time, quiet, the avoidance of noise or crowds, or having the chance to hears ones own thoughts or reflect or memory of a previous outdoor activity. It can allow moments of self reflection in Fi-like ways, or maybe make you wonder how you would feel taking the walk with someone else (Fe). So a sensory experience such as a walk in nature can have both Se and Si elements at play. So, that's my take on it.