Nothing's a perfect fit in MBTI. I'm just this weird INFP, ISFJ, ISFP hybrid. Socionics SEI fits me the best-I even have a round face and waddle like a duck. But yeah, I see SEI as sort of an ISFP and ISFJ hybrid, and I relate to their silliness, their quiet reflectiveness, and their taste for the finer things in life. Lower Ne still feels weird but I don't type ISFJ in MBTI so yeah, I guess it's fine. Enneagram definitely hits home, 9 and 4 are really relatable but SP 4 is probably the most relatable profile I've read. Withdrawn on it's own is really relatable, but 4s motivation really hits home as well as the SPs 4 need to be strong, their still waters run deep vibe and dauntless 4 is a good fit. The 4 temperaments, despite being a more simple system actually describe me really well. (Phleg-Mel). Phlegmatic's cynical humor, sluggishness and indecisiveness, and melancholics' idealism, broodiness, and yearning. Four temperaments was one of the first personality systems I learned about, which was 6 years ago. I remember how freakishly well it fit me, and it still does today.
Overall, I'd say socionics, followed by enneagram, fits me the best, even though alpha isn't a perfect fit(but I have heard that SEIs skew delta which fits). None of them are bad fits at all, save for my zodiac(I'm an Aries, I should be a Taurus or Pisces).