Exactly!! I swear, all ESFPs have Fe instead of Fi. it makes no sense
Uhh.... no, not in the least. ESFPs are in fact pretty far from any obvious display of Fe, unless you're just thinking Fe is all about emotional outbursts. Fe is not really a spontaneous function.
If you want mercurial displays of emotion, ESFP is the right place to start. Usually very positive and affirming and enthusiastic... until you cross their values and then BLAM, you might seem an amazing display of fireworks. Auxiliary Fe users definitely control all of their emotional displays and only let it out when appropriate; primary Fe users might do it, but it still tends to be based on failed expectations of the relationship or role the person plays in the situation and especially with ESFJ can revolve around someone failing to live up to the expectations set for them by their role in the community. ESFP usually blasts people for not treating them or someone else they way they feel they should have been treated (or given something they feel they deserved, or having their desires thwarted, etc), regardless of social role.
In my dealings with ENFP vs ESFP, what I notice most is that ENFP is much more likely to "get me" -- we connect on the Ne thing and see lots of possibilities and ramifications in situations. Possibility thinking, that's where we connect. But if I butt heads, it's usually when their Fi gets engaged -- they start indulging in possibilities I think are irrational because they tend to focus on possibilities that reflect what they already believe, where I just use Ne to feed my Ti hopper and Ti shreds any possibility that seems irrational. With ESFP, it's far more about me just experiencing something tangible with them -- doing things together and interacting, etc, having fun.
There's a sort of broad-scale almost spiritual aspect to NF Ne+Fi combos, whereas the Se+Fi comes off more as exuberance and just living life to the most passionate and most full. I think ESFP is much more driven emotionally by events unfolding in the surrounding environment, their mood can shift based on the mechanics of how a situation is unfolding; ENFP seems to have their moods driven more by how long-term events are unfolding, the direction things are going, what possibilities they see in the situation that are losing their opportunity to be made manifest.