Moved your post to this thread, where it's more on topic.
I would think that what you wear to interviews for each type of job would vary. Rule of thumb ... wear what the other people would wear in that job, but a notch up (just a bit more like the boss). Make it look like you are ready to work at the job you are applying for, but a bit nicer than what they would expect from you on a daily basis.
I would think that in showrooms you'd probably need to look more fashionable and/or trendy (depending on their lines) ... something like a pencil skirt and heels or a nice dress and maybe a jacket ... and a couple of tasteful but current accessories. You didn't say what your personal style was ... but it if matches the type of lines they carry in the showrooms, go for it. Whatever you wear, I'd say that you should try to emulate what they are selling: dressier and more expensive for a higher end line, a bit more simple for a lower end line, and trendier for juniors, etc. In showrooms they are either selling to retailers or helping stylists pull ... so look like you are in retail sales for that type of clothing.
For a production assistant, which I'm guessing is more about the dirty work of getting things manufactured and shippped, I'm thinking that maybe a just a bit more casual and more like you are ready to do the job ... jeans (if it's common that even the bosses wear jeans) or pants and more comfortable shoes. No fancy accessories (maybe just a watch and one other simple thing like a small pendant. a gold bangle or simple and conservative earrings like small hoops) especially if you are going to be doing physical stuff. If your work is just office stuff, you can be a bit showier, I would think ... but don't go too far ... it's production, not design or retail. Whatever you wear, show them that you are there to work.
Do some research if you can ... to determine what the usual "uniform" is at that company and/or in that line of work. Then use that as you jumping off place.
Re: your hair. Only you can decide if you are "compromising your personal preferences too much" ... I wouldn't want to advise on that.
I will say that I suspect that some interviewers may not like your natural braids ... but some will think it's just fine. It will depend on their own innate ideas about it, plus the general company atmosphere and how they perceive it will impact thier clients, if you are out in front of the public. If thier own image is conservative ... then then might not like it. But if they percieve their company as forward thinking and creative, it might actually be a plus. I suggest, as I did regarding dress, that you research these companies to see how they present themselves to the public and that might give you an idea about how they expect their employees to look. Being informed will help you decide what you want to do.
It depends on how badly you want the job. In general, I would say that if you want to be "safe", change it. An interview is a two way street ... they are determining how you will fit into their organization ... but you also need to figure out if this is the company where you will be happy. If you can't be happy if you cannot express yourself this way, just go as you are. Then if they hire you ... they hired the "real" you ... and you won't have to compromise.
