To me, Ni is about translating a theory/idea into the future....That is predicting the outcome before it arrives. As the repository of of data (Se) increases, an Ni user will gain insight in how a situation will unfold with increased precision. You ever think about a particular problem in which you are unable to solve at the moment, and later on have the answer arrive instantaneously. Ni is analogous to a derivative in calculus or the instantaneous rate of change. The only difference is that Ni is the instantaneous rate of insights.
Se (on the other hand) is about altering 3D space (reality) in some form and appreciating the external input derived from the 5 senses. Thus, Se users will gain a higher dopamine boost from immersing themselves in activities in which they can derive some form of pleasure from the senses relative to other functions. Now, Ne is not disjointed from Se in terms of independence ( Although Ne is paired with Si, it must follow that Se-->Si, not vice versa). The main difference is that Ne transcends the physical reality by formulating multiple instantaneous reactions (external insights) that are proportional to environmental stimulus, which feeds Si....
For instance, suppose you are staring at a blank wall for some time t....Ne activity will now be suppressed because the degree of environmental stimulus tends to 0. Thus, no impressions are created (Si-->0). Thus, there is a direct relationship between the degree of environmental stimulus and NE/SE activity....Yet Ne is always looking for new input to increase the repository of external insight (ideas, theories not directly tied/related to the initial input ...i.e: The heat unit of peppers is increased during Winter Months...hmmm, I wonder if that's connected to the human body which derives heat from peppers to fend off the cold or maybe the pepper contracts slightly to induce more heat per volume)...Hence, it should follow that NE users will act (explore outer world) because expanding their area of observation inevitably expands NE usage. SE users will also have ideas, yet these ideas are connected to the concrete world (translating, rotating 3D reality) because high Se implies that the five senses are well adapted to environmental stimulus meaning that more satisfaction will be gained by directly immersing themselves in some form of physical activity (But the satisfaction is derived from sensation seeking pleasures). Thus, activating their senses continuously brings fulfillment (traveling for the aspect of beauty, eating....) Our gravitation towards interests is function dependent....I spent some time once deriving Pi for fun because I was able explore the unknown in a novel way. I can also put my ideas to work, however, the initial stage is creating the theoretical framework of the idea to attempt predicting what the end result will be prior to testing the hypothesis. Strong Se users will experience a pulling effect due to the environment analogous to a radial (outward) force of gravity (hypothetical)...Therefore, there won't be much time between idealizing and the implementation stage due to their direct attraction towards physical space.
Now, if you envision the path of an idea/theory, then you have Ni in your stack. If you formulate multiple ideas/hypotheses on the run, then you have Ne in your stack. Creating PUNS is a great way to tell if someone uses NE (--i.e: A Plateau is the highest form of flattery--)