I'm asking about all of them: Myers Briggs, Enneagram, Keirsey, Big 5 etc.
The reason I am asking is because I don't want to be wasting my time if this is astrological type stuff. I want to be able to feel confident that my results are accurate so I can use them to move forward with my life. Finding a direction in life has been a huge problem for me and I'm tired of spinning my wheels.
Big 5 has a lot of science behind it. Try google scholar.
Enneagram is to a large extent astrology. It makes a lot of ungrounded claims.
Myers Briggs doesn't need science really, it makes no claims. You see, all the types generated by a MB test are like codes for the answers given. Now, the second step, attatching a personality description to that code, is actually something you should do yourself, but perhaps with the help of some insightful people.
Example: If I say my friend and my boss are both ESFPs, I am in essence saying that they would answer similarily to a certain set of questions. Now I can learn about stuff they have in common. When I meet a third person who I think is an ESFP, I have good grounds to assume that this person will also have the traits shared by my friend and my boss.
This is something you most likely already do, you already meet people with personalities you recognize and on those grounds assume to know something about the person. The only thing myers briggs does is put a name on the personalities which allows us to categorize and discuss personalities. So in this way, scientiific handling of relationships requires tools like MBTI, but MBTI does not require scientific proof, because it makes no claim, its only a framework. Atleast, that's how you should look at the myer briggs system, I know a lot of people try to take it further into astrology lane, so always think about what you're reading.