This explanation of Socionics isfp is as close to my thinking as any description has come. What type is closest in mbti do you think? It isn't istp, even isfp doesn't fit. Seems more like a laid back esfp to me.
Si as a base (1st) function (SEI and SLI)
A strong ability to recognize internal physical states in themselves and others, to understand how these states are reached, and to recreate and avoid these physical states.
Individuals who possess Si as a base function are drawn to situations that satisfy their inner physical experience. Whenever Si base function individuals are taking part in something that involves recognizing, recreating, or analyzing physical states, they feel a great deal of personal power and enthusiasm.
The avoidance of discomfort is one of the primary motivations of these types. Feelings of internal discomfort can arise from a tense psychological atmosphere, working too hard and sapping the body's resources, being pressured by other people or by numerous "things to do," and from unsatiated or oversatiated physical needs. These types tend to quickly recognize and be quite vocal about discomfort that arises and either take clever measures to dissipate it or simply get out of whatever is bothering them. They are very receptive to other people sharing feelings of discomfort with them and can help alleviate the tension and offer good solutions.
Si leading types are constantly adjusting themselves to their environment (which includes the people around them), and rarely have any fixed ideas about what is "appropriate" to desire in a given situation. Thus they are willing to accommodate other people's needs in an ad hoc manner. It is enough for something to "feel right" for them to justify doing it. This behavior may seem random to outside observers, since it is concomitant with weak Ni.
Fe as a creative (2nd) function (SEI and IEI)
The person is sensitive to the emotional atmosphere around him, either from an individual, or a group, or even from inanimate objects such as the landscape, the state of the physical environment he happens to be in, or his own emotional associations with the place or people around him. A positive emotional atmophere is essential for his sense of well being and inner peace, and he either tries to promote it himself by directly influencing it around him, or by simply moving away from the environment or the people causing a negative emotional environment in his view.
For the SEI, this takes an on-the-spot aspect and is reflected in cracking jokes, trying to make people laugh, or simply moving away from people he perceives as affecting him negatively. For the IEI, this takes a longer-term perspective; so the focus, rather than being on the immediate emotional environment, is on the perceived longer-term emotional state of others towards the individual, and is reflected in trying to be on good terms with those he interacts with or seeking distance or protection from, or "preventively" attacking, those he sees as irremediably hostile emotionally.