I believe the notions of breadth and depth are too fuzzy to apply to knowlwdge in a simle manner. I visualize it more like a web, or network, than a bunch of tree's that one goes down (up, whatever).
If you could manage to define a "congnitive distance measure," then "depth "of knowledge could be measured as the density of knowledge nodes in a particualr "congnitive area," while breadth could be measure by the overall (average) diameter of the whole knowledge network.
One weird thing, about knowledge for me is that lately, my urge to explain thigs (even when I am not qualified) is overwhelmeing. Is this my Ne starting to mature?
Accept the past. Live for the present. Look forward to the future. Robot Fusion
"As our island of knowledge grows, so does the shore of our ignorance." John Wheeler
"[A] scientist looking at nonscientific problems is just as dumb as the next guy." Richard Feynman
"[P]etabytes of  data is not the same thing as understanding emergent mechanisms and structures." Jim Crutchfield
^I would assume that would be a possibility. I often do that sometimes when bored just to see how I arrived at my hunches because it seems like I will just get this impulse that something is a certain way or means a certain thing. I think that is just natural Ti at work, but what I will then do is just list all the possible interpretations of a situation mentally or verbally. From there I just progress from words and definitions, to concepts, to analysis, to arguments.
This looks like just twisting words, nit picking, or bullshitting. To me its more like finding the smallest, barely visible crumble in the foundation and exploiting it. It's actually more like elaborating in the most elegant way I can reach before I'm abruptly stopped by a glare or look of contempt.
I think the urge to explain is just Ne coming out and being curious and trying to build a more complete picture. I definitely notice when I first get really excited, interested, or curious I will do the explain every little aspect and detail of things. It actually really does come out sounding like I'm defining, describing or explaining.
To sort of keep in line with OP I think that I like to find the particulars of topics that I'm interested in and just use my Ne to help Ti dig new holes. It seems like ENTP's would much rather focus on the much broader branching out concepts. I personally get more fun and enjoyment out of using Ne to just adjust my thinking till I find the fundamental issues and will stay on an interest just so I can get the rush of finding another little treasure no matter how long it takes.
My cold, snide, intellectual life is just a veneer, behind which lies the plywood of loneliness.