have your stuff

Hello,
Please help me understand the last part of the sentence. Could you explain it?

I do not know if people treat me differently because of my somewhat higher pitch voice. […]
If you are out in the real world facing challenges, whether you are a scientist or a business person or a doctor, sounding tough or _appearing to really have your stuff together has no actual bearing on your competence._

1. I can’t find what “have one’s stuff” means.
2. What does “together” refer to?
3. Is “competence” here a sufficient income to live on, the state of being qualified or sth else?

Thank you.

1. appearing to be organized, competent, prepared

"Have your act together" is another expression like that.

2. Having all the parts, talents, elements, etc. together in an organized way

3. I googled this and found it in a comment on NPR. I would substitute
"ability" for competence, but jmo.

In short, a person may look or appear to be competent, but that doesn't mean the person IS competent or incompetent (no bearing)...

1. If you have your stuff together, it means you are prepared and never appear to be unable to handle whatever task.

2. As is everything being ordered.

3. Actual work output (production).

Thanks a lot, K.T. and Guest.